Highly active compounds against COVID-19

ABSTRACT

The present invention is the use of purine nucleotide phosphoramidates or pharmaceutically acceptable salts thereof administered in an effective amount for the treatment or prevention of COVID-19, an infection caused by the SARS CoV-2 virus in a host, for example a human, in need thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/982,670, filed Feb. 27, 2020; U.S. Provisional Application No.62/994,206, filed Mar. 24, 2020; U.S. Provisional Application No.63/032,247, filed May 29, 2020; U.S. Provisional Application No.63/039,352, filed Jun. 15, 2020; U.S. Provisional Application No.63/040,985, filed Jun. 18, 2020; U.S. Provisional Application No.63/054,680, filed Jul. 21, 2020; U.S. Provisional 63/073,328 filed Sep.1, 2020; and, U.S. Provisional 63/146,456 filed Feb. 5, 2021. Theseapplications are incorporated by reference in their entireties for allpurposes.

FIELD OF THE INVENTION

The present invention is directed to the use of selected purinenucleotides and their pharmaceutically acceptable salts that haveadvantageous activity and dosage convenience for the treatment orprevention of the SARS-CoV-2 virus that causes COVID-19 in a host,typically a human, in need thereof.

BACKGROUND OF THE INVENTION

In December 2019, a number of patients in Wuhan, China were diagnosedwith pneumonia. These patients exhibited symptoms similar to the SARS(severe acute respiratory syndrome) outbreak in 2002-2003. In January2020, the infectious cause was identified as a novel coronavirus thatwas named severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)and the resulting disease called coronavirus disease 2019 (COVID-19).This potentially severe and sometimes lethal disease quickly spreadthroughout the world. On Mar. 11, 2020, the World Health Organizationdeclared COVID-19 a global pandemic.

The majority of patients infected with the SARS-CoV-2 virus exhibitmild, cold-like symptoms, including fever, cough, fatigue, shortness ofbreath, muscle aches, and loss of taste and/or smell. These symptomsusually resolve with minimal medical care in a few weeks. However,occasionally, symptoms persist for months. The virus may cause long-termdamage to the lungs, heart, and brain. Furthermore, in some patients,especially older adults, immunocompromised individuals, or those withunderlying conditions, the virus can cause severe symptoms that resultin hospitalization, ventilation, and/or death.

SARS-CoV-2 is a coronavirus (CoV), which is in the order Nidovirales,family Coronaviridae, subfamily Coronavirinae, which are envelopedviruses with a single-strand, positive-sense RNA genome. SARS-CoV-2 isapproximately 30 kilobases in size, which is among the largest known RNAgenomes. Related coronaviruses include severe acute respiratory syndromecoronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus(MERS-CoV). However, SARS-CoV-2 only shares 79.5% of its genome withSARS-CoV, and is therefore considered a new human-infectingbetacoronavirus (Zhou et al. Nature 2020, 579, 270) Compared to SARS-CoVand MERS-CoV, SARS-CoV-2 exhibits a faster human-to-human transmissionrate (Huang et al., Lancet 2000, 395, 497), making it particularlychallenging to contain and dangerous.

CoVs often originate as enzootic infections that cross the animal-humanspecies barrier and progress to establish zoonotic diseases in humans(Lau et al., PNAS 2005, 102, 14040-5; Rest et al., Infect Genet Evol.2003, 3, 219-25). Cross-species barrier jumps allowed CoVs such as theSARS CoV and the Middle Eastern respiratory syndrome CoV (MERS) tomanifest as virulent human viruses (Schoeman and Fielding, Virology2019, 16, 69). Similarly, genome sequencing has revealed that SARS-CoV-2is 96% identical at the whole-genome level to a bat coronavirus (Zhou etal. Nature 2020, 579, 270) and therefore most likely originated in bats.

SARS-CoV-2 enters human cells by binding to angiotensin convertingenzyme 2 (hACE2) receptors. Spike glycoproteins on the surface of thevirus envelope bind to the ACE2 receptor and then the humantransmembrane protease serine 2 cleaves and activates the spike protein,which allows SARS-CoV-2 to enter the cell through endocytosis or directfusion with the host membrane (Luan et al. Biochem. Biophys. Res.Commun. 2020: 527, 165; Hoffman, M. et al. Cell, 2020, 181, 271; Yang etal. Int. J. Biol. Sci. 2020, 16, 1724).

Once inside the cell, SARS-CoV-2 transcription and replication ismediated by a multi-subunit polymerase complex. The catalytic subunit ofthe complex is the RNA-dependent RNA polymerase (RdRp) known as nsp12.While the isolated nsp12 subunit is capable of conducting the polymerasereaction by itself, the presence of cofactors nsp7 and nsp8significantly increases the efficiency of the polymerase reaction (Ahnet al. Arch Virol. 2012, 157, 2095; Subissi et al. Proc. Natl. Acad.Sci., 2014, 111, E3900).

In April 2020, a crystal structure of the SARS-CoV-2 nsp-12, in complexwith nsp-7 and nsp-8, was resolved (Gao et al. Science 2020,368:779-782). The structure of nsp12 contains a polymerase C-terminalRdRp domain that is connected to an N-terminal extension domain referredto as the nidovirus RdRp-associated nucleotidyltransferase (NiRAN)domain. This NiRAN domain, which is conserved in all nidoviruses thatare able to conduct nucleotidylation activity, is characterized by an αand β fold composed of eight α helices and a five stranded β-sheet (Gaoet al. Science 2020, 368:779-782). The C-terminal domain has beencharacterized as a “cupped right hand” domain with finger, thumb, andpalm subdomains.

As the SARS-CoV-2 virus has spread throughout the world, it hasexhibited a high rate of mutation and a number of mutated forms of thevirus are circulating globally. These mutations have the potential toaffect the virus's ability to cause infections and the rate oftransmission. For example, the United Kingdom identified the B.1.1.7variant, which was named the Variant of Concern 202012/01 by PublicHealth England in the fall of 2020. This variant has eight mutations inthe spike region. There is evidence that this variant spreads morequickly and easily and may be associated with increased risk of death.In South Africa, other variants, B.1.351 and 501Y.V2, have beenidentified. Both variants share some mutations with the B.11.7 variant,including the N501Y mutation. Brazil has also identified a variant knownas P.1 that contains mutations that may affect the virus's ability to berecognized by antibodies. For this reason, it is important to developtherapies that are able to treat mutated forms of the virus, especiallythose with mutations on the spike protein.

The history of creating therapeutics for human coronavirus diseasesillustrates the complexity and challenges of the problem. There were nocommercial vaccines or drugs approved MERS-CoV and SARS-CoV despite thefact that the viruses were discovered in 2012 and 2003, respectively.

The lack of approved treatment, in combination with its high mortalityrate and its ease and speed of transmission, highlights the need for thedevelopment of an effective COVID-19 antiviral medication.

It is therefore an object of the present invention to provide compounds,compositions, and methods for the treatment and prevention of theSARS-CoV-2 virus that causes COVID-19.

SUMMARY OF THE INVENTION

The present invention provides a treatment for the SARS-CoV-2 virus in ahost in need thereof comprising administering an effective amount of aselected purine nucleotide compound as further described herein for theadvantageous treatment, prevention, or prophylaxis of the SARS-CoV-2virus that causes COVID-19. These purine nucleotides exhibit focusedactivity against the virus.

Further, and importantly, these compounds can be administered to hosts,such as humans, in need thereof, using a simple solid oral dosage formthat can be conveniently taken at home or generally outside of a medicalfacility without requiring parenteral administration or hospitalization.If desired or appropriate, the active compounds described herein canalternatively be administered parenterally or orally in a medicalfacility. The therapy can be used to treat mild, moderate or severedisease.

In one embodiment of the present invention, a compound of Formula I

or a pharmaceutically acceptable salt thereof, optionally in apharmaceutically acceptable carrier, is administered in an effectiveamount to a host, typically a human, in need thereof with COVID-19 or ahost at risk of infection or reinfection with the SARS-CoV-2 virus,i.e., as a prophylactic (and wherein the term prophylactic means totalprevention or minimization of acquired infection relative to diseasewithout such prophylactic treatment), wherein:

-   -   R¹ is selected from C₁-C₆alkyl, C₃-C₆cycloalkyl, and        —C(O)C₁-C₆alkyl;    -   R² is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₃₋₇cycloalkyl, or aryl (including phenyl and        napthyl) and in an alternative embodiment, R² is        aryl(C₁-C₄alkyl)-, heteroaryl, or heteroalkyl;    -   R³ is hydrogen or C₁₋₆alkyl (including methyl, ethyl, propyl,        and isopropyl);    -   R^(4a) and R^(4b) are independently selected from hydrogen,        C₁₋₆alkyl (including methyl, ethyl, propyl, and isopropyl), and        C₃₋₇cycloalkyl; and    -   R⁵ is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₁₋₆haloalkyl, or C₃₋₇cycloalkyl and in an        alternative embodiment, R⁵ is aryl(C₁-C₄alkyl)-, aryl,        heteroaryl, or heteroalkyl.

Non-limiting examples of C₁-C₆alkyl include methyl, ethyl, propyl,isopropyl, butyl, t-butyl, sec-butyl, isobutyl, —CH₂C(CH₃)₃,—CH(CH₂CH₃)₂, and —CH₂CH(CH₂CH₃)₂. Non-limiting examples ofC₃-C₆cycloalkyl include cyclopropyl, CH₂-cyclopropyl, cyclobutyl, andCH₂-cyclobutyl.

A non-limiting example of aryl(C₁-C₄alkyl)- is benzyl. A non-limitingexample aryl is phenyl.

In one embodiment, the SARS-CoV-2 virus is wild-type. In anotherembodiment, the SARS-CoV-2 virus has developed a natural or drug-inducedmutation, for example, but not limited to, a mutation in a viral proteinselected from an envelope (E) protein, membrane (M) protein, spike (S)protein, nsp1, nsp2, nsp3, nsp4, nsp5, nsp 6, nsp7, nsp8, nsp9, nsp10,nsp12, nsp13, nsp14, nsp15, nsp16, ORF1ab, ORF3a, ORF6, ORF7a, ORF7b,ORF8, and ORF10.

A non-limiting example of a compound of Formula I is Compound 1 or apharmaceutically acceptable salt thereof. In one embodiment, Compound 1or a pharmaceutically acceptable salt thereof, optionally in apharmaceutically acceptable carrier, is administered to a host in needthereof, such as a human, infected with SARS-CoV-2, or to a host at riskof infection with the SARS-CoV-2 virus, i.e., as a prophylactic.

Compound 1 is depicted above without regard to stereochemistry at thephosphorus atom, which is chiral. Compound 1 can be used either withoutregard to stereochemistry at the phosphorus, or a phosphoro-racemicform, or with any desired ratio of phosphorus R- and S-enantiomers ofthe compound, including enantiomerically enriched (i.e., up to at least90%, 95%, 98%, 99%, or even 100% free of the opposite enantiomer, whichare in fact diastereomers because there are multiple chiral carbons inthe molecule). Compound 1A is the S-enantiomer and Compound 1B is theR-enantiomer.

Compound 1, including Compound 1A and Compound 1B are potent inhibitorsagainst COVID-19 caused by the SARS-CoV-2 virus. As described in Example5 and Example 6, Compound 1A exhibits an EC₉₀ value of 0.64 μM againstSARS-Cov-2 in HAE cells (human airway epithelial cells). The assay usingHAE cells is an in vitro model of the lung and is a representativesystem for SARS-CoV-2 replication. It has also surprisingly beendiscovered that the active triphosphate metabolite of Compound 1A isrobustly formed when exposed to normal primary bronchial and nasalepithelial cells. As described in Example 7, when Compound 1A wasincubated in human nasal and bronchial epithelial cells, the half-lifeof the active triphosphate species is greater than 1.5 days in bothbronchial and nasal epithelial cells. This could not have been predictedin advance and is especially important in treating patients with earlystages of the infection when the virus is heavily concentrated in thenasal and bronchial cells.

The data herein presented shows that the compound concentrates in thelung over the liver, and the previously reported data confirms that thecompounds also preferentially concentrate in the liver over the heart(see for example, Example 19 of PCT Application PCT/US2018/016301).Taken together, this data confirms that the compound concentrates in thetarget organ, the lung, over the liver or heart, reducing toxicity

In one embodiment, Compound 1, such as Compound 1A or Compound 1B or apharmaceutically acceptable salt thereof, optionally in apharmaceutically acceptable carrier, is administered in an effectiveamount to a host, for example, a human, in need thereof infected withthe SARS-CoV-2 virus, or a host at risk of infection with the SARS-CoV-2virus, i.e., as a prophylactic. In one embodiment, the pharmaceuticallyacceptable salt is a hemi-sulfate salt, shown below as Compound 2,Compound 2A, and Compound 2B:

As described in Example 8, Compound 2A was administered to non-humanprimates and the intracellular concentration of the active triphosphatespecies was measured in lung, kidney, and liver cells. Surprisingly, theactive triphosphate metabolite concentrates in the lung over the liver(Table 8) and the half-life of the active metabolite in the lung is 9.4hours (FIG. 7A). This is important because COVID-19 typically presentsas a respiratory illness. In fact, the active triphosphate speciesconcentration is 1.6 times higher in the lung than the liver after twicea day oral administration of 30 mg/kg of Compound 2A.

Furthermore, the compounds of the present invention may inhibitSARS-CoV-2 infection via a unique mechanism of action that accounts forhigh selectivity. CoV viral replication is achieved at the RNA-dependentRNA polymerase (RdRp) nsp12 subunit, which is activated by co-factorsnsp7 and nsp8. As discussed in Example 6, there is a 30-fold differencein Compound 1A activity against SARS-CoV-2 and MERS-CoV, even thoughMERS-CoV and other CoVs, such as SARS-CoV-1 and SARS-CoV-2, do notexhibit significant structural differences at the RdRp active site. Thissuggests that polymerase inhibition is not the sole basis fordifferential activity against these viruses.

COVID-19 is an acute viral infection for which antiviral therapeuticsmay be effective within the first stage of the infection when viral loadis at its maximum and there is rapid viral replication initially innasal, throat and pulmonary cells. The availability of a potent, safe,oral antiviral administered to individuals infected with SARS-CoV-2 inthe early stages of the disease has the potential to avert clinicalillness, minimize long term damage, and mitigate the COVID-19 pandemic.As described above, it has been shown that selected compounds of thepresent invention are able to concentrate in the lungs over the liver.This is therapeutically beneficial when treating patients in the firststages of infection with the SARS-CoV-2 pathogen when it is desirable toprevent or lessen late-stage viral damage. High concentrations in thelung over the heart and liver is also therapeutically beneficial fortreating patients in later stages of the infection.

The present invention also includes the use of a compound of Formula IIin an effective amount to treat or prevent COVID-19 disease caused bythe SARS-CoV-2 virus in a host in need thereof as described herein:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   R¹ is selected from C₁-C₆alkyl, C₃-C₆cycloalkyl, and        —C(O)C₁-C₆alkyl;    -   R² is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₃₋₇cycloalkyl, or aryl (including phenyl and        napthyl) and in an alternative embodiment, R² is        aryl(C₁-C₄alkyl)-, heteroaryl, or heteroalkyl;    -   R³ is hydrogen or C₁₋₆alkyl (including methyl, ethyl, propyl,        and isopropyl);    -   R^(4a) and R^(4b) are independently selected from hydrogen,        C₁₋₆alkyl (including methyl, ethyl, propyl, and isopropyl), and        C₃₋₇cycloalkyl; and    -   R⁵ is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₁₋₆haloalkyl, or C₃₋₇cycloalkyl and in an        alternative embodiment, R⁵ is aryl(C₁-C₄alkyl)-, aryl,        heteroaryl, or heteroalkyl.

In one embodiment, a compound of Formula II or a pharmaceuticallyacceptable salt thereof, optionally in a pharmaceutically acceptablecarrier, is administered in an effective amount to a host in needthereof infected with the SARS-CoV-2 virus, or to a host at risk ofinfection or reinfection with the SARS-CoV-2 virus, i.e., as aprophylactic.

A non-limiting example of a compound of Formula II is Compound 3 or apharmaceutically acceptable salt thereof.

In one embodiment, Compound 3 or a pharmaceutically acceptable saltthereof, optionally in a pharmaceutically acceptable carrier, isadministered in an effective amount to a host in need thereof infectedwith the SARS-CoV-2 virus, or to a host at risk of infection with theSARS-CoV-2 virus, i.e., as a prophylactic. Compound 3 can be used in aphosphoro-racemic form, or with any desired ratio of phosphorus R- andS-enantiomers of the compound, including enantiomerically enrichedmaterial up to pure enantiomers. Compound 3A is the S-enantiomer andCompound 3B is the R-enantiomer.

An additional non-limiting example of Formula II includes Compound 4.Alternative configurations of Compound 4 include Compound 4A andCompound 4B. In one embodiment, Compound 4, optionally in apharmaceutically acceptable carrier, is administered in an effectiveamount to a host in need thereof infected with the SARS-CoV-2 virus orto a host at risk of infection, i.e., as a prophylactic.

The present invention also includes the use of a compound of Formula IIIto treat or prevent COVID-19 disease caused by the SARS-CoV-2 virus in ahost in need thereof as described herein:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   X is selected from C₁-C₃haloalkyl (including C₁₋₃fluoroalkyl and        C₁₋₃chloroalkyl, such as CH₂F, CHF₂, CF₃, CH₂CF₃, CH₂CHF₂,        CH₂CH₂F, CF₂CH₃, CF₂CF₃, and CH₂Cl), C₂-C₄alkenyl, C₂-C₄alkynyl,        and C₁-C₃hydroxyalkyl; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

In one embodiment, the compound of Formula III to treat or preventCOVID-19 disease is a compound or a pharmaceutically acceptable saltthereof of Formula IIIa, Formula IIIb, Formula IIIc, Formula IIId,Formula IIIe, or Formula IIIf:

The present invention also includes the use of a compound of Formula IVin an effective amount to treat or prevent COVID-19 disease caused bythe SARS-CoV-2 virus in a host in need thereof as described herein:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   X is selected from C₁-C₃haloalkyl (including C₁-C₃fluoroalkyl        and C₁₋₃chloroalkyl, such as CH₂F, CHF₂, CF₃, CH₂CF₃, CH₂CHF₂,        CH₂CH₂F, CF₂CH₃, CF₂CF₃, and CH₂Cl), C₂-C₄alkenyl, C₂-C₄alkynyl,        and C₁-C₃hydroxyalkyl; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

In one embodiment, the compound of Formula IV to treat or preventCOVID-19 disease is a compound or a pharmaceutically acceptable saltthereof of Formula IVa, Formula IVb, Formula IVc, Formula IVd, FormulaIVe, or Formula IVf:

The present invention also includes the use of a compound of Formula Vin an effective amount to treat or prevent COVID-19 disease caused bythe SARS-CoV-2 virus in a host in need thereof as described herein:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   Y and Y′ are independently selected from Cl and F; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

Non-limiting examples of a compound of Formula V include

The present invention also includes the use of a compound of Formula VIto treat or prevent COVID-19 in a host in need thereof as describedherein:

wherein

-   -   R⁶ is selected from hydrogen, —C(O)R^(6A), —C(O)OR^(6A),        C₁₋₆alkyl, and —CH₂—O—R^(6A) and in an alternative embodiment,        —C(O)NR^(6B)R^(6C);    -   R^(6A) is selected from hydrogen, C₁₋₆alkyl, C₁-C₆haloalkyl (for        example, —CHCl₂, —CCl₃, —CH₂Cl, —CF₃, —CHF₂, —CH₂F), aryl, and        aryl(C₁₋₆alkyl)- wherein the aryl group is optionally        substituted with a substituent selected from alkoxy, hydroxy,        nitro, bromo, chloro, fluoro, azido, and haloalkyl, and in an        alternative embodiment, R^(6A) is selected from C₁₋₂₀alkyl and        C₂₋₂₀alkenyl;    -   R^(6B) and R^(6C) are independently selected from hydrogen,        C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl, aryl(C₁₋₆alkyl)-, heteroaryl,        and heteroarylalkyl wherein the C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl,        aryl(C₁₋₆alkyl)-, heteroaryl, and heteroarylalkyl can optionally        be substituted with at least one substituent selected from        alkoxy (including but not limited to methoxy and ethoxy),        hydroxy, nitro, bromo, chloro, fluoro, azido, and haloalkyl;    -   R⁷ is NH₂, H, or —NR⁸R⁹;    -   R⁸ and R⁹ are independently selected from hydrogen, C₁₋₆alkyl,        —C(O)R^(6A), and —C(O)OR^(6A);    -   Y is selected from F and Cl;    -   Z is selected from methyl, C₁-C₃haloalkyl (including        C₁₋₃fluoroalkyl and C₁₋₃chloroalkyl, such as CH₂F, CHF₂, CF₃,        CH₂CF₃, CH₂CHF₂, CH₂CH₂F, CF₂CH₃, CF₂CF₃, and CH₂Cl),        C₂-C₄alkenyl, C₂-C₄alkynyl, C₁-C₃hydroxyalkyl, and halogen        (including Cl and F), and in an alternative embodiment, Z is        C₁₋₄alkyl; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

Non-limiting examples of R⁶ include

Additional non-limiting examples of R⁶ include:

Additional non-limiting examples of R⁶ include:

Additional non-limiting examples of R⁶ include:

Non-limiting examples of a compound of Formula VI include

The present invention also includes the use of a compound of Formula VIIto treat or prevent COVID-19 in a host in need thereof as describedherein:

wherein

-   -   B is selected from

-   -   R⁶ is selected from hydrogen, —C(O)R^(6A), —C(O)OR^(6A),        C₁₋₆alkyl, and —CH₂—O—R^(6A) and in an alternative embodiment,        —C(O)NR^(6B)R^(6C);    -   R^(6A) is selected from hydrogen, C₁₋₆alkyl, C₁-C₆haloalkyl (for        example, —CHCl₂, —CCl₃, —CH₂Cl, —CF₃, —CHF₂, —CH₂F), aryl, and        aryl(C₁₋₆alkyl)- wherein the aryl group is optionally        substituted with a substituent selected from alkoxy, hydroxy,        nitro, bromo, chloro, fluoro, azido, and haloalkyl and in an        alternative embodiment, R^(6A) is selected from C₁₋₂₀alkyl and        C₂₋₂₀alkenyl;    -   R^(6B) and R^(6C) are independently selected from hydrogen,        C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl, aryl(C₁₋₆alkyl)-, heteroaryl,        and heteroarylalkyl wherein the C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl,        aryl(C₁₋₆alkyl)-, heteroaryl, and heteroarylalkyl can optionally        be substituted with at least one substituent selected from        alkoxy (including but not limited to methoxy and ethoxy),        hydroxy, nitro, bromo, chloro, fluoro, azido, and haloalkyl;    -   R⁷ is NH₂, H, or —NR⁸R⁹;    -   R⁸ and R⁹ are independently selected from hydrogen, C₁₋₆alkyl,        —C(O)R^(6A), and —C(O)OR^(6A);    -   Y is selected from F and Cl;    -   Z is selected from methyl, C₁-C₃haloalkyl (including        C₁₋₃fluoroalkyl and C₁₋₃chloroalkyl, such as CH₂F, CHF₂, CF₃,        CH₂CF₃, CH₂CHF₂, CH₂CH₂F, CF₂CH₃, CF₂CF₃, and CH₂Cl),        C₂-C₄alkenyl, C₂-C₄alkynyl, C₁-C₃hydroxyalkyl, and halogen        (including Cl and F), and in an alternative embodiment Z is        C₁₋₄alkyl;    -   R⁴⁰ is selected from H, C₁₋₃alkoxy, C₁₋₃alkyl, N₃, CN, and        halogen (including Cl and F);    -   R⁴¹ is selected from H, C₁₋₃alkyl (including methyl) and halogen        (including Cl, F, and Br);    -   R^(42a) and R^(42b) are independently selected from C₁₋₃alkyl        (including methyl), NH₂, H, —NR⁸R⁹, and —C(O)NR⁸R⁹; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

In one embodiment, the invention also includes a compound of FormulaVIIa, Formula VIIb, Formula VIIc, and Formula VIId:

Non-limiting examples of B include:

Non-limiting examples of compounds of Formula VII include:

The present invention also includes the use of a compound of FormulaVIII, Formula IX, or Formula X wherein R¹⁰ is a monophosphate, adiphosphate, a triphosphate, or R^(10A) wherein R^(10A) is a stabilizedphosphate prodrug that metabolizes in vivo to a monophosphate,diphosphate, or triphosphate to treat or prevent COVID-19 disease in ahost in need thereof as described herein:

wherein

-   -   R¹⁰ is selected from

-   -    and R^(10A);    -   R^(10A) is a stabilized phosphate prodrug that metabolizes in        vivo to a monophosphate, diphosphate, or triphosphate;    -   R¹¹ is selected from hydrogen and R¹; and    -   R¹ is selected from C₁-C₆alkyl, C₃-C₆cycloalkyl, and        —C(O)C₁-C₆alkyl.

Non-limiting examples of compounds of Formula VIII, Formula IX, orFormula X include:

Additional non-limiting examples of compounds of Formula VIII, FormulaIX, or Formula X include:

The phosphorus in any of the Formulas described herein may be chiral andthus can be provided as an R or S enantiomer or mixture thereof,including a racemic mixture. The compound is typically at least 90% freeof the opposite enantiomer, and can be at least 95%, 96%, 97%, 98%, 99%or even 100% free of the opposite enantiomer. Unless describedotherwise, the compound is at least 90% free of the opposite enantiomer.For example, Compound 1 is depicted without regard to stereochemistry atthe phosphorus atom, which is chiral. Compound 1 can be used in aracemic form, or with any desired ratio of phosphorus R_(p)- andS_(p)-enantiomers of the compound, including enantiomerically enrichedmaterial up to pure enantiomers. Compound 1A has S-stereochemistry atthe phosphorus and Compound 1B has R-stereochemistry at the phosphorus.In some embodiments, Compound 1 is used in a form at least 90% free ofthe opposite enantiomer, and can be at least 98%, 99% or even 100% freeof the opposite enantiomer. For example, Compound 1A can be at least90%, 95%, 98%, 99%, or even 100% free of the opposite R_(p)-enantiomer.Alternatively, Compound 1B can be at least 90%, 95%, 98%, 99%, or even100% free of the opposite S_(p)-enantiomer.

Similarly, Compound 2 is depicted without regard to stereochemistry atthe phosphorus atom, which is chiral. Compound 2 can be used in aracemic form, or with any desired ratio of phosphorus R- andS-enantiomers of the compound, including enantiomerically enrichedmaterial up to pure enantiomers. Compound 2A has S-stereochemistry atthe phosphorus and Compound 2B has R-stereochemistry at the phosphorus.In some embodiments, Compound 2 is used in a form at least 90% free ofthe opposite enantiomer, and can be at least 98%, 99% or even 100% freeof the opposite enantiomer. In one embodiment, Compound 2A can be atleast 90%, 95%, 98%, 99%, or even 100% free of the oppositeR_(p)-enantiomer. In one embodiment, Compound 2B can be at least 90%,95%, 98%, 99%, or even 100% free of the opposite S_(p)-enantiomer.

Unless described otherwise, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII drawn with regard tostereochemistry at the phosphorus atom is at least 90% free of theopposite enantiomer.

Compounds, compositions, dosage forms, and methods are provided for thetreatment of COVID-19 caused by the SARS-CoV-2 virus in a host in needthereof via administration of an effective amount of a compound ofFormula I, Formula II, Formula III, Formula IV, Formula V, Formula VI,Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof. In one embodiment, a compoundof Formula I, Formula II, Formula III, Formula IV, Formula V, FormulaVI, Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII ora pharmaceutically acceptable salt thereof can also be used in aneffective amount prophylactically to prevent or restrict the progressionof COVID-19 in a host in need thereof who has been exposed to the virusor who is at risk of infection or reinfection.

The weight of active compound in the dosage form described herein iswith respect to either the free form or the salt form of the compoundunless otherwise specifically indicated. For example, approximately 600mg of Compound 2 is the equivalent of approximately 550 mg ofCompound 1. In one non-limiting embodiment, a loading dose is 1100mg/day (free base) (i.e., 1200 mg/day hemisulfate salt of Compound 1),and a maintenance dose is 550 mg/day (free base) (i.e, 600 mg/day ofhemisulfate salt)). In one embodiment, the loading dose is administeredonce and the maintenance dose is administered twice a day for at least3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 days.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof is administered in a dosage form of at least about 100,200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850,900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450,1500, 1550, 1600, 1650, or 1700 mg. In certain embodiments, a compoundof Formula I, Formula II, Formula III, Formula IV, Formula V, FormulaVI, Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII ora pharmaceutically acceptable salt thereof is administered at a dose ofat least 250 mg, 500 mg, at least 600 mg, at least 700 mg, at least 800mg, at least 900 mg, at least 1000 mg, at least 1100 mg, at least 1200mg, at least 1300 mg, at least 1400 mg or at least 1500 mg.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof, including Compound 1 or a pharmaceutically acceptablesalt, is administered in a dosage form of about 550 mg once day.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof, including Compound 1 or a pharmaceutically acceptable saltthereof, is administered in a dosage form of about 600 mg once a day.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof is administered in a dosage form of about 550 mg twice aday.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof is administered in a dosage form of about 600 mg twice aday.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof is administered in a dosage form of about 550 mg twice aday for at least five days, optionally with the standard of care. In oneembodiment, Compound 1 or a pharmaceutically acceptable salt thereof isadministered in a dosage form of about 550 mg twice a day for at leastfive days, optionally with the standard of care. In one embodiment,Compound 1 is Compound 1A. In one embodiment, Compound 1 is Compound 1B.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof is administered in a dosage form of about 600 mg twice aday for at least of days, optionally with the standard of care. In oneembodiment, Compound 2 or a pharmaceutically acceptable salt thereof isadministered in a dosage form of about 600 mg twice a day for at leastfive days, optionally with the standard of care. In one embodiment,Compound 2 is Compound 2A. In one embodiment, Compound 2 is Compound 2B.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof is administered in a dosage form of about 550 mg twice aday for at least about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, or more days, optionally with the standard of care. In oneembodiment, Compound 1 or a pharmaceutically acceptable salt thereof isadministered in a dosage form of about 550 mg twice a day for at leastabout 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or more days,optionally with the standard of care.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof is administered in a dosage form of about 600 mg twice aday for at least about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, or more days, optionally with the standard of care. In oneembodiment, Compound 2 or a pharmaceutically acceptable salt thereof isadministered in a dosage form of about 600 mg twice a day for at leastabout 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or more days,optionally with the standard of care.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof, for example Compound 1 or Compound 3 or a pharmaceuticallyacceptable salt thereof, including Compound 2 or Compound 4, isadministered at an initial dose (or loading dose) followed by amaintenance dose, wherein the loading dose is at the discretion of thephysician based on the severity of the presented disease and the size ofthe patient. In certain embodiments, the loading dose is about or atleast 1.5 times greater, about or at least 2 times greater, about or atleast 2.5 times greater, or about or at least 3 times greater than themaintenance dose. In one embodiment, the loading dose is administeredonce, twice, three, four, or more times before the first maintenancedose, and may be given once, twice, three, or four times a day asinstructed by the physician.

In one embodiment, a compound of Formula I, Formula II, Formula III,Formula IV, Formula V, Formula VI, Formula VII, Formula VIII, FormulaIX, Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, for example Compound 1 or Compound 3 or a pharmaceuticallyacceptable salt thereof, including Compound 2 or Compound 4, isadministered at a daily loading dose (which can be provided in one orseveral dosages throughout the day) of at least about 800 mg, at leastabout 900 mg, at least about 1000 mg, at least about 1100 mg, at leastabout 1200 mg, at least about 1300 mg, or at least about 1400 mgfollowed by a maintenance dose of at least about 300 mg, at least about350 mg, at least about 400 mg, at least about 450 mg, at least about 500mg, at least about 550 mg, at least about 600 mg, at least about 650 mg,at least about 700 mg, or at least about 750 mg and the maintenance doseis taken once, twice, or three times a day. In one embodiment, themaintenance dose is taken twice a day, and optionally over 1, 2, 3, or 4days. In one embodiment, the maintenance dose is thereafter administered1, 2 or 3 times a day for at least about 4 days, at least about 5 days,at least about 6 days, at least about 7 days, at least about 8 days, atleast about 9 days, at least about 10 days, at least about 15 days, atleast about 20 days, at least about 25 days, or more.

In certain embodiments, Compound 1 or Compound 3 or a pharmaceuticallyacceptable salt thereof, including Compound 2 or Compound 4, isadministered at a dose of at least about 300 mg, at least about 350 mg,at least about 400 mg, at least about 450 mg, at least about 500 mg, atleast about 550 mg, at least about 650, or at least about 750 and thedose is taken once, twice, or three times a day.

In one embodiment, Compound 1 or a pharmaceutically acceptable saltthereof, for example Compound 2, is administered at a dose of at leastabout 500 mg, at least about 550 mg, or at least 600 mg and the dose istaken twice daily. In one embodiment, Compound 1 or a pharmaceuticallyacceptable salt thereof, for example Compound 2, is administered at aloading dose of at least about 1000 mg, at least about 1100 mg, or atleast about 1200 mg followed by a maintenance dose of at least about 500mg, at least about 550 mg, or at least 600 mg twice daily.

In one embodiment, the maintenance dose is administered for at leastabout 4, 5, 6, 7, 8, 9, 10, or more days. In one embodiment, Compound 1is Compound 1A. In one embodiment, Compound 1 is Compound 1B. In oneembodiment, Compound 2 is Compound 2A. In one embodiment, Compound 2 isCompound 2B.

In one embodiment, Compound 1 is administered at a dose of at about 550mg and the dose is taken twice daily. In one embodiment, Compound 1 isCompound 1A. In one embodiment, Compound 1 is Compound 1B.

In one embodiment, Compound 2 is administered at a dose of at about 600mg and the dose is taken twice daily. In one embodiment, Compound 2 isCompound 2A. In one embodiment, Compound 2 is Compound 2B.

In certain embodiments, the method of the present invention includesadministering a compound as described herein, such as Formula I, FormulaII, Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof, for example Compound 1 or Compound 2, once,twice, three, or four or more times a day as necessary to treat theinfection. In one embodiment, a compound of Formula I, Formula II,Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof, for example Compound 1 or Compound 2, isadministered for at least about 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, ormore days, or for a length of time at the discretion of a healthcareprovider.

Alternatively, the compound can be administered for a time period thatis appropriate to avoid infection or reduce the severity of an infectionof a human or other animal at risk of becoming infected with the virus.

In one embodiment, the compound of the present invention is administeredindefinitely until the risk of infection or reinfection no longer exits.In one embodiment, a compound of Formula I, Formula II, Formula III,Formula IV, Formula V, Formula VI, Formula VII, Formula VIII, FormulaIX, Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof is administered for at least 1 month, at least 2 months, atleast 3 months, at least 4 months, at least 5 months, or at least 6months or more. In certain embodiments, a compound of Formula I, FormulaII, Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof is administered once, twice, three, or four ormore times a day.

In another alternative embodiment, a method to prevent transmission isprovided that includes administering an effective amount of one of thecompounds described herein to a human in need thereof for a sufficientlength of time prior to exposure to a high risk situation, includingduring travel or public events or meetings, or if the host is in a highrisk group, including for example, up to 3, 5, 7, 10, 12, 14 or moredays prior to a communicable situation, and then during and optionallyafter the potential exposure. Alternatively, the selected compound asdescribed herein can be administered for an indefinite period in amaintenance dosage to protect a person in a high-risk environment.

The present invention also includes compounds of Formula XI and FormulaXII:

or a pharmaceutically acceptable salt thereof

wherein

-   -   R^(12a) and R^(12b) are oxygen protecting groups and at least        one of R^(12a) and R^(12b) is —C(O)OC₁₋₆ alkyl, for example        —C(O)OtBu, or —C(O)O-benzyl wherein the alkyl and benzyl group        can be optionally substituted with a substituent selected from        alkoxy, hydroxy, nitro, bromo, chloro, fluoro, azido, and        haloalkyl.

In one embodiment, R^(12a) is —C(O)OC₁₋₆alkyl or —C(O)O-benzyl andR^(12b) is an oxygen protecting group which when attached to the oxygenis an ester, ether, or silyl ether moiety. In an alternative embodiment,R^(12b) is —C(O)OC₁₋₆alkyl or —C(O)O-benzyl and R^(12a) is an oxygenprotecting group which when attached to the oxygen is an ester, ether,or silyl ether moiety. In one embodiment, R^(12a) and R^(12b) are both—C(O)OC₁₋₆alkyl, for example —C(O)OtBu. In one embodiment, R^(12a) andR^(12b) are both —C(O)O-benzyl.

In one embodiment, a compound of Formula XII is Formula XIIA:

In one embodiment, a compound of Formula XII is Formula XIIB:

The present invention thus includes the following features:

-   -   (a) A method for the treatment of COVID-19 caused by the        SARS-CoV-2 virus in a host in need thereof comprising        administering an effective amount of a compound of Formula I,        Formula II, Formula III, Formula IV, Formula V, Formula VI,        Formula VII, Formula VIII, Formula IX, Formula X, or Formula        XIII or a pharmaceutically acceptable salt thereof, optionally        in a pharmaceutically carrier;    -   (b) A method for the prevention or minimization of COVID-19 in a        host in need thereof comprising administering an effective        amount of a compound of Formula I, Formula II, Formula III,        Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,        Formula IX, Formula X, or Formula XIII or a pharmaceutically        acceptable salt thereof, optionally in a pharmaceutically        carrier;    -   (c) The method of (b) for the prevention or minimization of        reinfection by the SARS-CoV-2 virus or contracting COVID-19 in a        host in need thereof,    -   (d) The method of (a)-(c) wherein the compound is Compound 1;    -   (e) The method of (a)-(c) wherein the compound is Compound 1A;    -   (f) The method of (a)-(c) wherein the compound is Compound 1B;    -   (g) The method of (a)-(c) wherein the compound is Compound 2;    -   (h) The method of (a)-(c) wherein the compound is Compound 2A;    -   (i) The method of (a)-(c) wherein the compound is Compound 2B;    -   (j) The method of (a)-(c) wherein the compound is Compound 3;    -   (k) The method of (a)-(c) wherein the compound is Compound 3A;    -   (l) The method of (a)-(c) wherein the compound is Compound 3B;    -   (m) The method of (a)-(c) wherein the compound is Compound 4;    -   (n) The method of (a)-(c) wherein the compound is Compound 4A;    -   (o) The method of (a)-(c) wherein the compound is Compound 4B;    -   (p) The method of (a)-(c) wherein the compound is of Formula        IIIa;    -   (q) The method of (a)-(c) wherein the compound is of Formula        IIIb;    -   (r) The method of (a)-(c) wherein the compound is of Formula        IIIc;    -   (s) The method of (a)-(c) wherein the compound is of Formula        IIId;    -   (t) The method of (a)-(c) wherein the compound is of Formula        IIIe;    -   (u) The method of (a)-(c) wherein the compound is of Formula        IIIf;    -   (v) The method of (a)-(c) wherein the compound is of Formula        IVa;    -   (w) The method of (a)-(c) wherein the compound is of Formula        IVb;    -   (x) The method of (a)-(c) wherein the compound is of Formula        IVc;    -   (y) The method of (a)-(c) wherein the compound is of Formula        IVd;    -   (z) The method of (a)-(c) wherein the compound is of Formula        IVe;    -   (aa) The method of (a)-(c) wherein the compound is of Formula        IVf;    -   (bb) The method of (a)-(c) wherein the compound is of Formula V;    -   (cc) The method of (a)-(c) wherein the compound is of Formula        VI;    -   (dd) The method of (a)-(c) wherein the compound is of Formula        VII;    -   (ee) The method of (a)-(c) wherein the compound is of Formula        VIII, Formula IX, or Formula X;    -   (ff) A compound of Formula I, Formula II, Formula III, Formula        IV, Formula V, Formula VI, Formula VII, Formula VIII, Formula        IX, Formula X, or Formula XIII or a pharmaceutically acceptable        salt thereof for use to treat a COVID-19 infection caused by the        SARS-CoV-2 virus in a host in need thereof, optionally in a        pharmaceutically acceptable carrier;    -   (gg) A compound of Formula I, Formula II, Formula III, Formula        IV, Formula V, Formula VI, Formula VII, Formula VIII, Formula        IX, Formula X, or Formula XIII or a pharmaceutically acceptable        salt thereof for use to prevent or minimize (relative to without        treatment) an infection caused by the SARS-CoV-2 virus in a host        in need thereof, optionally in a pharmaceutically acceptable        carrier;    -   (hh) The compound of (gg) to prevent a reinfection caused by the        SARS-CoV-2 virus in a host in need thereof;    -   (ii) The use of a compound of Formula I, Formula II, Formula        III, Formula IV, Formula V, Formula VI, Formula VII, Formula        VIII, Formula IX, Formula X, or Formula XIII or a        pharmaceutically acceptable salt thereof, optionally in a        pharmaceutically acceptable carrier, in the manufacture of a        medicament for the treatment of the 2019 coronavirus disease        (COVID-19) caused by the SARS-CoV-2 virus;    -   (jj) The use of a compound of Formula I, Formula II, Formula        III, Formula IV, Formula V, Formula VI, Formula VII, Formula        VIII, Formula IX, Formula X, or Formula XIII or a        pharmaceutically acceptable salt thereof, optionally in a        pharmaceutically acceptable carrier, in the manufacture of a        medicament for the prevention of COVID-19 caused by the        SARS-CoV-2 virus in a host in need thereof;    -   (kk) The use of (jj) to prevent a reinfection caused by the        SARS-CoV-2 virus in a host in need thereof;    -   (ll) Any of the above embodiments, wherein the pharmaceutically        acceptable carrier is in a dosage form suitable for oral        administration;    -   (mm) The dosage form of (ll) wherein the dosage form is a solid        dosage form;    -   (nn) The dosage form of (mm) in the form of a tablet;    -   (oo) The dosage form of (mm) in the form of a capsule;    -   (pp) The dosage form of (ll) wherein the dosage form is a liquid        dosage form;    -   (qq) The dosage form of (pp) in the form of a solution or a        suspension;    -   (rr) Any of embodiments (a)-(kk), wherein the pharmaceutically        acceptable carrier is in a dosage form suitable for intravenous        administration;    -   (ss) Any of embodiments (a)-(kk), wherein the pharmaceutically        acceptable carrier is in a dosage form suitable for parenteral        administration;    -   (tt) Any of the above embodiments, wherein a compound of Formula        I, Formula II, Formula III, Formula IV, Formula V, Formula VI,        Formula VII, Formula VIII, Formula IX, Formula X, or Formula        XIII or a pharmaceutically acceptable salt thereof is        administered once a day;    -   (uu) Any of the above embodiments, wherein a compound of Formula        I, Formula II, Formula III, Formula IV, Formula V, Formula VI,        Formula VII, Formula VIII, Formula IX, Formula X, or Formula        XIII or a pharmaceutically acceptable salt thereof is        administered twice a day;    -   (vv) Any of the above embodiments, wherein a compound of Formula        I, Formula II, Formula III, Formula IV, Formula V, Formula VI,        Formula VII, Formula VIII, Formula IX, Formula X, or Formula        XIII or a pharmaceutically acceptable salt thereof is        administered three times a day;    -   (ww) Any of the above embodiments, wherein a compound of Formula        I, Formula II, Formula III, Formula IV, Formula V, Formula VI,        Formula VII, Formula VIII, Formula IX, Formula X, or Formula        XIII or a pharmaceutically acceptable salt thereof is        administered for at least one week, ten days, two weeks, three        weeks, one month, at least two months, at least three months, at        least four months, at least five months, or at least six months        or more.    -   (xx) Any of the above embodiments, wherein a compound of Formula        I, Formula II, Formula III, Formula IV, Formula V, Formula VI,        Formula VII, Formula VIII, Formula IX, Formula X, or Formula        XIII or a pharmaceutically acceptable salt thereof is        administered at least once, at least twice, or at least three        times a day indefinitely until the risk of infection no longer        exists;    -   (yy) Any of the above embodiments, wherein a compound of Formula        I, Formula II, Formula III, Formula IV, Formula V, Formula VI,        Formula VII, Formula VIII, Formula IX, Formula X, or Formula        XIII or a pharmaceutically acceptable salt thereof is        administered at a dose of at least about 400 mg;    -   (zz) Any of the above embodiments, wherein a compound of Formula        I, Formula II, Formula III, Formula IV, Formula V, Formula VI,        Formula VII, Formula VIII, Formula IX, Formula X, or Formula        XIII or a pharmaceutically acceptable salt thereof is        administered at a dose of at least about 500 mg;    -   (aaa) Any of the above embodiments, wherein a compound of        Formula I, Formula II, Formula III, Formula IV, Formula V,        Formula VI, Formula VII, Formula VIII, Formula IX, Formula X, or        Formula XIII or a pharmaceutically acceptable salt thereof is        administered at a dose of at least about 550 mg;    -   (bbb) Any of the above embodiments, wherein a compound of        Formula I, Formula II, Formula III, Formula IV, Formula V,        Formula VI, Formula VII, Formula VIII, Formula IX, Formula X, or        Formula XIII or a pharmaceutically acceptable salt thereof is        administered at a dose of at least about 600 mg;    -   (ccc) A method for the treatment of COVID-19 in a host in need        thereof comprising administering Compound 1, wherein Compound 1        is administered at a dose of at least about 550 mg and the dose        is administered twice a day;    -   (ddd) A method for the treatment of COVID-19 virus in a host in        need thereof comprising administering Compound 1, wherein        Compound 1 is administered at a loading dose of at least about        1100 mg followed by a maintenance dose of at least about 550 mg        twice a day;    -   (eee) Embodiment (ccc or ddd) wherein Compound 1 is Compound 1A;    -   (fff) Embodiment (ccc or ddd) wherein Compound 1 is Compound 1B;    -   (ggg) A method for the treatment of COVID-19 in a host in need        thereof comprising administering Compound 2, wherein Compound 2        is administered at a dose of at least about 600 mg and the dose        is administered twice a day;    -   (hhh) A method for the treatment of COVID-19 in a host in need        thereof comprising administering Compound 2, wherein Compound 2        is administered at a loading dose of at least about 1200 mg        followed by a maintenance dose of at least about 600 mg twice a        day;    -   (iii) Embodiment (ggg or hhh) wherein Compound 2 is Compound 2A;    -   (jjj) Embodiment (ggg or hhh) wherein Compound 2 is Compound 2B;    -   (kkk) A compound of Formula II or a pharmaceutically acceptable        salt thereof;    -   (lll) Compound 4 or a pharmaceutically acceptable salt as        described herein;    -   (mmm) Compound 4A and Compound 4B as described herein;    -   (nnn) A pharmaceutical formulation comprising an effective        amount of a compound of Formula II, optionally in a        pharmaceutically acceptable carrier.    -   (ooo) A compound of Formula XI or Formula XII;    -   (ppp) A compound of Formula XIIA;    -   (qqq) A compound of Formula XIIB;    -   (rrr) A compound of Formula VII;    -   (sss) A compound of Formula VIIa;    -   (ttt) A compound of Formula VIIb;    -   (uuu) A compound of Formula VIIc;    -   (vvv) A compound of Formula VIId; and    -   (www) A pharmaceutical composition comprising an effective        amount of a compound of Formula VIIa, Formula VIIb, Formula        VIIc, or Formula VIId.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a graph of the concentration of triphosphate Compound 1-6 inhuman bronchial and nasal epithelial cells after exposure to 10 μM ofCompound 1A as described in Example 7. The half-life of Compound 1-6 inbronchial cells and nasal cells was 39 hours and 38 hours, respectively.The x-axis is the time post-washout measured in hours and the y-axis isthe concentration of Compound 1-6 in pmol/million cells.

FIG. 2 is a graph comparing the triphosphate Compound 1-6 levels inhuman bronchial epithelial cells following exposure to Compound 1A (1A),ALS-8112 (ALS), and the 4′-Me substituted prodrug isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-2,4-dimethyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(4′-Me) as described in Example 7. The x-axis is the time post-washoutmeasured in hours and the y-axis is the concentration of Compound 1-6 inpmol/million cells.

FIG. 3 is a graph comparing the triphosphate Compound 1-6 levels inhuman nasal epithelial cells following exposure to Compound 1A (1A),ALS-8112 (ALS), and 4′-Me substituted prodrug isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-2,4-dimethyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(4′-Me) as described in Example 7. The x-axis is the time post-washoutmeasured in hours and the y-axis is the concentration of Compound 1-6 inpmol/million cells.

FIG. 4 is a graph of the mean plasma profile of Compound 1A in monkeysadministered 30 mg/kg oral doses of Compound 2A twice a day (BID) for 3days as described in Example 8. The x-axis is the time post-dosemeasured in hours and the y-axis is the plasma concentration of Compound1A measured in ng/mL.

FIG. 5 is a graph of the mean plasma profile of metabolite Compound 1-2in monkeys administered 30 mg/kg oral doses of Compound 2A twice a day(BID) for 3 days as described in Example 8. The x-axis is the timepost-dose measured in hours and the y-axis is the plasma concentrationof Compound 1-2 measured in ng/mL.

FIG. 6 is a graph of the mean plasma profile of triphosphate surrogatemetabolite Compound 1-7 in monkeys administered 30 mg/kg oral doses ofCompound 2A twice a day (BID) for 3 days as described in Example 8. Thex-axis is the time post-dose measured in hours and the y-axis is theplasma concentration of Compound 1-7 measured in ng/mL.

FIG. 7A is a graph of the triphosphate Compound 1-6 concentration inlung, kidney, and liver tissue in monkeys following administration of 30mg/kg oral doses of Compound 2A twice a day (BID) for 3 days asdescribed in Example 8. The half-life in the lung, kidney, and liver was9.4 hours, 8.0 hours, and 4.3 hours, respectively. The x-axis is thetime post-dose measured in hours and the y-axis is the tissueconcentration of Compound 1-6 measured in ng/g.

FIG. 7B is a graph of triphosphate Compound 1-6 concentration in lung,kidney, and liver tissue in monkeys following administration of 30 mg/kgoral doses of Compound 2A twice a day (BID) for 3 days as described inExample 8. The tissue concentration of Compound 1-6 is shown 2 hours, 12hours, 24 hours, and 48 hours post last dose. The x-axis is time postthe last dose measured in hours and the y-axis is tissue concentrationmeasured in μM.

FIG. 8 is a graph of levels of triphosphate Compound 1-6 in hepatocytesincubated with Compound 2A as described in Example 9 and previouslydescribed in from Good, S. S. et al. 2020 PLoS ONE 15(1):e0227104. Theconcentration was 7 times higher in human hepatocytes than in monkeys.The x-axis is the incubation time measured in hours and the y-axis isthe Compound 1-6 concentration measured in pmol/10⁶ cells.

FIG. 9 is the simulation of intracellular concentrations of Compound 1-6in human lung tissue as described in Example 10. The predicted lungconcentration is based on predicted trough (C_(12h)) steady-state plasmaCompound 1-7, a plasma surrogate for intracellular triphosphate Compound1-6, (Berliba, e. et al. 2019 Antimicrob. Agents Chemother.63(12):e01201-19) in humans multiplied by a ratio of 1.6 (thetriphosphate concentration in the lung is 1.6 times greater than in theliver at steady-state trough levels as described in Example 8). Thex-axis is time measured in days and the y-axis is simulated lungCompound 1-6 concentration measured in M.

FIG. 10 is a stimulation of intracellular concentrations of Compound 1-6in human lung tissue using the two approaches as described in Example10. The solid curve represents predicted lung concentrations of theactive triphosphate Compound 1-6 metabolite after correcting for theCompound 1-6 lung-to-liver concentration ratio of 1.6. The dotted curverepresents predicted lung concentrations of the active triphosphateCompound 1-6 metabolite after correcting for the Compound 1-6lung-to-Compound 1-7 plasma ratio of 1.2. The horizontal line representsthe EC₉₀ of Compound 1A against SARS-CoV-2 in HAE cells in vitro (0.47μM). The x-axis is time measured in days and the y-axis is simulatedlung Compound 1-6 concentration measured in μM.

FIG. 11 is an illustration of a compound of Formula I, which can also beadministered as a pharmaceutically acceptable salt.

DETAILED DESCRIPTION OF THE INVENTION

The invention disclosed herein is a method for the treatment orprevention of the 2019 coronavirus disease (COVID-19) caused by theSARS-CoV-2 virus in a host, for example a human, in need thereofcomprising administering an effective amount of a compound of Formula Ior a pharmaceutically acceptable salt thereof:

wherein

-   -   R¹ is selected from C₁-C₆alkyl, C₃-C₆cycloalkyl, and        —C(O)C₁-C₆alkyl;    -   R² is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₃₋₇cycloalkyl, or aryl (including phenyl and        napthyl) and in an alternative embodiment, R² is        aryl(C₁-C₄alkyl)-, heteroaryl, or heteroalkyl;    -   R³ is hydrogen or C₁₋₆alkyl (including methyl, ethyl, propyl,        and isopropyl);    -   R^(4a) and R^(4b) are independently selected from hydrogen,        C₁₋₆alkyl (including methyl, ethyl, propyl, and isopropyl), and        C₃₋₇cycloalkyl; and    -   R⁵ is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₁₋₆haloalkyl, or C₃₋₇cycloalkyl and in an        alternative embodiment, R⁵ is aryl(C₁-C₄alkyl)-, aryl,        heteroaryl, or heteroalkyl.

Non-limiting examples of a compound of Formula I include Compound 1 andCompound 2. In one embodiment, the compounds are administered as theS-enantiomer, such as Compound 1A. In one embodiment, the compounds areadministered as the R-enantiomer, such as Compound 1B. In oneembodiment, a compound of Formula I is Compound 2, Compound 2A, orCompound 2B.

Alternative configurations of Compound 1 or a pharmaceuticallyacceptable salt thereof that can be used include:

Alternative configurations of Compound 2 that can be used include:

Additional alternative configurations of Compound 1 or apharmaceutically acceptable salt thereof, for example, Compound 2 thatcan be used include:

Non-limiting examples of a compound of Formula I include:

or a pharmaceutically acceptable salt thereof.

Additional non-limiting examples of a compound of Formula I include:

or a pharmaceutically acceptable salt thereof.

Additional non-limiting examples of compounds of Formula I include:

or a pharmaceutically acceptable salt thereof.

The present invention also includes the use of an effective amount of acompound of Formula II to treat or prevent COVID-19 disease caused bythe SARS-CoV-2 virus in a host in need thereof:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   R¹ is selected from C₁-C₆alkyl, C₃-C₆cycloalkyl, and        —C(O)C₁-C₆alkyl;    -   R² is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₃₋₇cycloalkyl, or aryl (including phenyl and        napthyl) and in an alternative embodiment, R² is        aryl(C₁-C₄alkyl)-, heteroaryl, or heteroalkyl;    -   R³ is hydrogen or C₁₋₆alkyl (including methyl, ethyl, propyl,        and isopropyl);    -   R^(4a) and R^(4b) are independently selected from hydrogen,        C₁₋₆alkyl (including methyl, ethyl, propyl, and isopropyl), and        C₃₋₇cycloalkyl; and    -   R⁵ is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₁₋₆haloalkyl, or C₃₋₇cycloalkyl and in an        alternative embodiment, R⁵ is aryl(C₁-C₄alkyl)-, aryl,        heteroaryl, or heteroalkyl.

In one embodiment, a compound of Formula II or a pharmaceuticallyacceptable salt thereof, optionally in a pharmaceutically acceptablecarrier, is administered in an effective amount to a host in needthereof with COVID-19, or at risk of infection with the SARS-CoV-2virus, i.e., as a prophylactic.

Non-limiting examples of a compound of Formula II include Compound 3 andCompound 4. In one embodiment, the compounds are administered as theS-enantiomer, such as Compound 3A and Compound 4A. In one embodiment,the compounds are administered as the R-enantiomer, such as Compound 3Bor Compound 4B.

Alternative configurations of Compound 3 or a pharmaceuticallyacceptable salt thereof include:

Additional alternative configurations of Compound 4 include:

Additional alternative configurations of Compound 3 or apharmaceutically acceptable salt thereof, for example, Compound 4 thatcan be used include:

Non-limiting examples of a compound of Formula II include:

or a pharmaceutically acceptable salt thereof.

Additional non-limiting examples of a compound of Formula II include:

or a pharmaceutically acceptable salt thereof.

Additional non-limiting examples of compounds of Formula II include:

or a pharmaceutically acceptable salt thereof.

The present invention also includes the use of an effective amount of acompound of Formula III to treat or prevent COVID-19 disease caused bythe SARS-CoV-2 virus in a host in need thereof:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   R¹ is selected from C₁-C₆alkyl, C₃-C₆cycloalkyl, and        —C(O)C₁-C₆alkyl;    -   R² is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₃₋₇cycloalkyl, or aryl (including phenyl and        napthyl) and in an alternative embodiment, R² is        aryl(C₁-C₄alkyl)-, heteroaryl, or heteroalkyl;    -   R³ is hydrogen or C₁₋₆alkyl (including methyl, ethyl, propyl,        and isopropyl);    -   R^(4a) and R^(4b) are independently selected from hydrogen,        C₁₋₆alkyl (including methyl, ethyl, propyl, and isopropyl), and        C₃₋₇cycloalkyl; and    -   R⁵ is hydrogen, C₁₋₆alkyl (including methyl, ethyl, propyl, and        isopropyl), C₁₋₆haloalkyl, or C₃₋₇cycloalkyl and in an        alternative embodiment, R⁵ is aryl(C₁-C₄alkyl)-, aryl,        heteroaryl, or heteroalkyl; and    -   X is selected from C₁-C₃haloalkyl (including C₁₋₃fluoroalkyl and        C₁₋₃chloroalkyl, such as CH₂F, CHF₂, CF₃, CH₂CF₃, CH₂CHF₂,        CH₂CH₂F, CF₂CH₃, CF₂CF₃, and CH₂Cl), C₂-C₄alkenyl, C₂-C₄alkynyl,        and C₁-C₃hydroxyalkyl.

In one embodiment, the compound of Formula III to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus in a host in needthereof is a compound of Formula IIIa:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IIIa, R¹ is methyl.

In one embodiment of Formula IIIa, R¹ is cyclopropyl.

In one embodiment of Formula IIIa, R² is phenyl.

In one embodiment of Formula IIIa, R² is napthyl.

In one embodiment of Formula IIIa, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IIIa, R⁵ is isopropyl.

In one embodiment of Formula IIIa, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIa, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIa, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IIIa include:

Additional non-limiting examples of a compound of Formula IIIa include:

In one embodiment, the compound of Formula III to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus in a host in needthereof is a compound of Formula IIIb.

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IIIb, Re is methyl.

In one embodiment of Formula IIIb, R¹ is cyclopropyl.

In one embodiment of Formula IIIb, R² is phenyl.

In one embodiment of Formula IIIb, R² is napthyl.

In one embodiment of Formula IIIb, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IIIb, R⁵ is isopropyl.

In one embodiment of Formula IIIb, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIb, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIb, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IIIb include:

Additional non-limiting examples of a compound of Formula IIIb include:

In one embodiment, the compound of Formula III to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus in a host in needthereof is a compound of Formula IIIc:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IIIc, R¹ is methyl.

In one embodiment of Formula IIIc, R¹ is cyclopropyl.

In one embodiment of Formula IIIc, R² is phenyl.

In one embodiment of Formula IIIc, R² is napthyl.

In one embodiment of Formula IIIc, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IIIc, R⁵ is isopropyl.

In one embodiment of Formula IIIc, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIc, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIc, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IIIc include:

Additional non-limiting examples of a compound of Formula IIIc include:

In one embodiment, the compound of Formula III to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus in a host in needthereof is a compound of Formula IIId:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IIId, R¹ is methyl.

In one embodiment of Formula IIId, R¹ is cyclopropyl.

In one embodiment of Formula IIId, R² is phenyl.

In one embodiment of Formula IIId, R² is napthyl.

In one embodiment of Formula IIId, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IIId, R⁵ is isopropyl.

In one embodiment of Formula IIId, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIId, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIId, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IIId include:

Additional non-limiting examples of a compound of Formula IIId include:

In one embodiment, the compound of Formula III to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus in a host in needthereof is a compound of Formula IIIe:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IIIe, R¹ is methyl.

In one embodiment of Formula IIIe, R¹ is cyclopropyl.

In one embodiment of Formula IIIe, R² is phenyl.

In one embodiment of Formula IIIe, R² is napthyl.

In one embodiment of Formula IIIe, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IIIe, R⁵ is isopropyl.

In one embodiment of Formula IIIe, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIe, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIe, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IIIe include:

Additional non-limiting examples of a compound of Formula IIIe include:

In one embodiment, the compound of Formula III to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus in a host in needthereof is a compound of Formula IIIf:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IIIf, R¹ is methyl.

In one embodiment of Formula IIIf, R¹ is cyclopropyl.

In one embodiment of Formula IIIf, R² is phenyl.

In one embodiment of Formula IIIf, R² is napthyl.

In one embodiment of Formula IIIf, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IIIf, R⁵ is isopropyl.

In one embodiment of Formula IIIf, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIf, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IIIf, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IIIf include:

Additional non-limiting examples of a compound of Formula IIIe include:

Non-limiting examples of a compound of Formula III include:

The present invention also includes the use of a compound of Formula IVto treat or prevent COVID-19 disease caused by the SARS-CoV-2 virus in ahost in need thereof as described herein:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   X is selected from C₁-C₃haloalkyl (including C₁₋₃fluoroalkyl and        C₁₋₃chloroalkyl, such as CH₂F, CHF₂, CF₃, CH₂CF₃, CH₂CHF₂,        CH₂CH₂F, CF₂CH₃, CF₂CF₃, and CH₂Cl), C₂-C₄alkenyl, C₂-C₄alkynyl,        and C₁-C₃hydroxyalkyl; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

In one embodiment, the compound of Formula IV to treat or preventCOVID-19 disease is a compound or a pharmaceutically acceptable saltthereof of Formula IVa, Formula IVb, Formula IVc, Formula IVd, FormulaIVe, or Formula IVf:

In one embodiment, the compound of Formula IV to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus is a compound of FormulaIVa:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IVa, R¹ is methyl.

In one embodiment of Formula IVa, R¹ is cyclopropyl.

In one embodiment of Formula IVa, R² is phenyl.

In one embodiment of Formula IVa, R² is napthyl.

In one embodiment of Formula IVa, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IVa, R⁵ is isopropyl.

In one embodiment of Formula IVa, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVa, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

Non-limiting examples of a compound of Formula IVa include:

In one embodiment, the compound of Formula IV to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus is a compound of FormulaIVb:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IVb, R¹ is methyl.

In one embodiment of Formula IVb, R¹ is cyclopropyl.

In one embodiment of Formula IVb, R² is phenyl.

In one embodiment of Formula IVb, R² is napthyl.

In one embodiment of Formula IVb, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IVb, R⁵ is isopropyl.

In one embodiment of Formula IVb, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVb, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

Non-limiting examples of a compound of Formula IVb include:

In one embodiment, the compound of Formula IV to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus is a compound of FormulaIVc:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IVc, R¹ is methyl.

In one embodiment of Formula IVc, R¹ is cyclopropyl.

In one embodiment of Formula IVc, R² is phenyl.

In one embodiment of Formula IVc, R² is napthyl.

In one embodiment of Formula IVc, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IVc, R⁵ is isopropyl.

In one embodiment of Formula IVc, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVc, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVc, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IVc include:

In one embodiment, the compound of Formula IV to treat or preventCOVID-19 disease is a compound of Formula IVd:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IVd, R¹ is methyl.

In one embodiment of Formula IVd, R¹ is cyclopropyl.

In one embodiment of Formula IVd, R² is phenyl.

In one embodiment of Formula IVd, R² is napthyl.

In one embodiment of Formula IVd, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IVd, R⁵ is isopropyl.

In one embodiment of Formula IVd, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVd, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVd, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IVd include:

In one embodiment, the compound of Formula IV to treat or preventCOVID-19 disease is a compound of Formula IVe:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IVe, R¹ is methyl.

In one embodiment of Formula IVe, R¹ is cyclopropyl.

In one embodiment of Formula IVe, R² is phenyl.

In one embodiment of Formula IVe, R² is napthyl.

In one embodiment of Formula IVe, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IVe, R⁵ is isopropyl.

In one embodiment of Formula IVe, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVe, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVe, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula We include:

The one embodiment, the compound of Formula IV to treat or preventCOVID-19 disease caused by the SARS-CoV-2 virus is a compound of FormulaIVf:

or a pharmaceutically acceptable salt thereof.

In one embodiment of Formula IVf, R¹ is methyl.

In one embodiment of Formula IVf, R¹ is cyclopropyl.

In one embodiment of Formula IVf, R² is phenyl.

In one embodiment of Formula IVf, R² is napthyl.

In one embodiment of Formula IVf, R^(4a) is hydrogen and R^(4b) ismethyl.

In one embodiment of Formula IVf, R⁵ is isopropyl.

In one embodiment of Formula IVf, the compound is the S_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVf, the compound is the R_(p)-isomer andthe phosphoramidate is in the L-configuration.

In one embodiment of Formula IVf, the pharmaceutically acceptable saltis the hemi-sulfate salt.

Non-limiting examples of a compound of Formula IVf include:

The present invention also includes the use of a compound of Formula Vto treat or prevent COVID-19 disease caused by the SARS-CoV-2 virus asdescribed herein:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   Y and Y′ are independently selected from Cl and F; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

In one embodiment of Formula IV, Y′ is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is F, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is F, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is Cl, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is Cl, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is Cl, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is Cl, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is Cl, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl,and R⁵ is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is Cl, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is F, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is F, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is F, Y is Cl, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula IV, Y′ is F, Y is Cl, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

Non-limiting examples of a compound of Formula V include

Additional non-limiting examples of Formula V include

The present invention also includes the use of a compound of Formula VIto treat or prevent COVID-19 in a host n need thereof as describedherein:

wherein

-   -   R⁶ is selected from hydrogen, —C(O)R^(6A), —C(O)OR^(6A),        C₁₋₆alkyl, and —CH₂—O—R^(6A) and in an alternative embodiment,        —C(O)NR^(6B)R^(6C);    -   R^(6A) is selected from hydrogen, C₁₋₆alkyl, C₁-C₆haloalkyl (for        example, —CHCl₂, —CCl₃, —CH₂Cl, —CF₃, —CHF₂, —CH₂F), aryl, and        aryl(C₁₋₆alkyl)- wherein the aryl group is optionally        substituted with a substituent selected from alkoxy, hydroxy,        nitro, bromo, chloro, fluoro, azido, and haloalkyl and in an        alternative embodiment, R^(6A) is selected from C₁₋₂₀alkyl and        C₂₋₂₀alkenyl;    -   R^(6B) and R^(6C) are independently selected from hydrogen,        C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl, aryl(C₁₋₆alkyl)-, heteroaryl,        and heteroarylalkyl wherein the C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl,        aryl(C₁₋₆alkyl)-, heteroaryl, and heteroarylalkyl can optionally        be substituted with at least one substituent selected from        alkoxy (including but not limited to methoxy and ethoxy),        hydroxy, nitro, bromo, chloro, fluoro, azido, and haloalkyl;    -   R⁷ is NH₂, H, or —NR⁸R⁹;    -   R⁸ and R⁹ are independently selected from hydrogen, C₁₋₆alkyl,        —C(O)R^(6A), and —C(O)OR^(6A);    -   Y is selected from F and Cl;    -   Z is selected from methyl, C₁-C₃haloalkyl (including        C₁₋₃fluoroalkyl and C₁₋₃chloroalkyl, such as CH₂F, CHF₂, CF₃,        CH₂CF₃, CH₂CHF₂, CH₂CH₂F, CF₂CH₃, CF₂CF₃, and CH₂Cl),        C₂-C₄alkenyl, C₂-C₄alkynyl, C₁-C₃hydroxyalkyl, and halogen        (including Cl and F), and in an alternative embodiment Z is        C₁₋₄alkyl; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

Non-limiting examples of R⁶ include

In one embodiment of Formula VI, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁷R⁹.

In one embodiment of Formula VI, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₃, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₃, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CF₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CF₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CF₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CF₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CF₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CF₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CF₃, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CF₃, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is Cl, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is Cl, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₂F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CH₂F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CH₂F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CH₂F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CH₂F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CH₂F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₂F, Y is F, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl,and R⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₂F, Y is F, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CHCH₂, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CH₂CH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CH₂CH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CH₂CH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CH₂CH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CHCH₂, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CHCH₂, Y is F, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl,and R⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CHCH₂, Y is F, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CCH, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CCH, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is F, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is F, Y is F, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CH₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CH₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CH₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CH₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CH₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₃, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl,and R⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₃, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CF₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CF₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CF₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CF₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CF₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CF₃, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CF₃, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl,and R⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CF₃, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is Cl, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is Cl, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is Cl, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is Cl, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is Cl, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is Cl, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is Cl, Y is Cl, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, andR⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is Cl, Y is Cl, R¹ is cyclopropyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₂F, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CH₂F, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CH₂F, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CH₂F, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CH₂F, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CH₂F, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₂F, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl,and R⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CH₂F, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CHCH₂, Y is Cl, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CH₂CH, Y is Cl, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CH₂CH, Y is Cl, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CH₂CH, Y is Cl, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CH₂CH, Y is Cl, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CHCH₂, Y is Cl, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CHCH₂, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl,and R⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CHCH₂, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CCH, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NH₂.

In one embodiment of Formula VI, Z is CCH, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is H.

In one embodiment of Formula VI, Z is CCH, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NR⁸R⁹.

In one embodiment of Formula VI, Z is CCH, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)R^(6A).

In one embodiment of Formula VI, Z is CCH, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, and R⁷ is NHC(O)OR^(6A).

In one embodiment of Formula VI, Z is CCH, Y is Cl, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵ isC₁-C₆alkyl.

In one embodiment of Formula VI, Z is CCH, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl,and R⁵ is C₁-C₆alkyl.

In one embodiment of Formula VI, Z is CCH, Y is Cl, R¹ is cyclopropyl,R² is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is methyl, and R⁵is C₁-C₆alkyl.

Non-limiting examples of a compound of Formula VI include

Additional non-limiting examples of a compound of Formula VI include:

The present invention also includes the use of a compound of Formula VIIto treat or prevent COVID-19 in a host in need thereof as describedherein:

wherein

-   -   B is selected from

-   -   R⁶ is selected from hydrogen, —C(O)R^(6A), —C(O)OR^(6A),        C₁₋₆alkyl, and —CH₂—O—R^(6A) and in an alternative embodiment,        —C(O)NR^(6B)R^(6C);    -   R^(6A) is selected from hydrogen, C₁₋₆alkyl, C₁-C₆haloalkyl (for        example, —CHCl₂, —CCl₃, —CH₂Cl, —CF₃, —CHF₂, —CH₂F), aryl, and        aryl(C₁₋₆alkyl)- wherein the aryl group is optionally        substituted with a substituent selected from alkoxy, hydroxy,        nitro, bromo, chloro, fluoro, azido, and haloalkyl and in an        alternative embodiment, R^(6A) is selected from C₁₋₂₀alkyl and        C₂₋₂₀alkenyl;    -   R^(6B) and R^(6C) are independently selected from hydrogen,        C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl, aryl(C₁₋₆alkyl)-, heteroaryl,        and heteroarylalkyl wherein the C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl,        aryl(C₁₋₆alkyl)-, heteroaryl, and heteroarylalkyl can optionally        be substituted with at least one substituent selected from        alkoxy (including but not limited to methoxy and ethoxy),        hydroxy, nitro, bromo, chloro, fluoro, azido, and haloalkyl;    -   R⁷ is NH₂, H, or —NR⁸R⁹;    -   R⁸ and R⁹ are independently selected from hydrogen, C₁₋₆alkyl,        —C(O)R^(6A), and —C(O)OR^(6A);    -   Y is selected from F and Cl;    -   Z is selected from methyl, C₁-C₃haloalkyl (including        C₁₋₃fluoroalkyl and C₁₋₃chloroalkyl, such as CH₂F, CHF₂, CF₃,        CH₂CF₃, CH₂CHF₂, CH₂CH₂F, CF₂CH₃, CF₂CF₃, and CH₂Cl),        C₂-C₄alkenyl, C₂-C₄alkynyl, C₁-C₃hydroxyalkyl, and halogen        (including Cl and F), and in an alternative embodiment Z is        C₁₋₄alkyl;    -   R⁴⁰ is selected from H, C₁₋₃alkoxy, C₁₋₃alkyl, N₃, CN, and        halogen (including Cl and F);    -   R⁴¹ is selected from H, C₁₋₃alkyl (including methyl) and halogen        (including Cl, F, and Br);    -   R^(42a) and R^(42b) are selected from C₁₋₃alkyl (including        methyl), NH₂, H, —NR⁸R⁹, and —C(O)NR⁸R⁹; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

Non-limiting examples of B include:

In one embodiment, the invention also includes a compound of FormulaVIIa, Formula VIIb, Formula VIIc, and Formula VIId:

In one embodiment of Formula VII, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is CH₃, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is Cl, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is CH₂F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is CH₂F, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is CH₂F, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is CH₂F, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is CH₂F, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is CH₂F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is CH₂F, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is CH₂F, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is CH₂F, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is CH₂F, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is CHCH₂, Y is F, R¹ is methyl, R²is aryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is CCH, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is hydrogen; and B is

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

In one embodiment of Formula VII, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R¹ is C₁₋₆alkyl and R⁷ is NH₂. In a furtherembodiment, R¹ is methyl and R⁷ is NH₂.

In one embodiment of Formula VIIa, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is C₁₋₆alkyl and R^(42a) is H. In a furtherembodiment, R⁴¹ is methyl and R^(42a) is H. In a further embodiment, R⁴¹is C₁₋₆alkyl and R^(42a) is NH₂. In a further embodiment, R⁴¹ is methyland R^(42a) is NH₂.

In one embodiment of Formula VIIb, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b) isC₁₋₆alkyl. In a further embodiment, R⁴¹ is H, R^(42a) is H, and R^(42b)is methyl. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) isNH₂, and R^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ isC₁₋₆alkyl or H, R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In afurther embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, andR^(42b) is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl orH, R^(42a) is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIIc, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B is

In a further embodiment, R⁴¹ is H, R^(42a) is NH₂, and R^(42b) is H. Ina further embodiment, R⁴¹ is H, R^(42a) is —NHCH₃, and R^(42b) is H. Ina further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is NH₂, and R^(42b)is C₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H,R^(42a) is —NR⁸R⁹, and R^(42b) is C₁₋₆alkyl or H. In a furtherembodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a) is —NHCH₃, and R^(42b) isC₁₋₆alkyl or H. In a further embodiment, R⁴¹ is C₁₋₆alkyl or H, R^(42a)is —NHCH₃, and R^(42b) is NH₂.

In one embodiment of Formula VIId, Z is F, Y is F, R¹ is methyl, R² isaryl, R³ is hydrogen, R^(4a) is hydrogen, R^(4a) is C₁-C₄alkyl, R⁵ isC₁-C₆alkyl, R⁶ is hydrogen, R⁴⁰ is cyano or nitro; and B

In a further embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NR⁸R⁹. In afurther embodiment, R⁴¹ is halogen and R^(42a) is —C(O)NHCH₃. In afurther embodiment, R⁴¹ is Br and R^(42a) is —C(O)NR⁸R⁹. In a furtherembodiment, R⁴¹ is Br and R^(42a) is —C(O)NHCH₃.

Non-limiting examples of compounds of Formula VII include:

The present invention also includes the use of a compound of FormulaVIII, Formula IX, or Formula X wherein R¹⁰ is a monophosphate, adiphosphate, a triphosphate, or R^(10A) wherein R^(10A) is a stabilizedphosphate prodrug that metabolizes in vivo to a monophosphate,diphosphate, or triphosphate to treat or prevent COVID-19 disease in ahost in need thereof as described herein:

wherein

-   -   R¹⁰ is selected from

-   -    and R^(10A);    -   R^(10A) is a stabilized phosphate prodrug that metabolizes in        vivo to a monophosphate, diphosphate, or triphosphate;    -   R¹¹ is selected from hydrogen and R¹; and    -   R¹ is selected from C₁-C₆alkyl, C₃-C₆cycloalkyl, and        —C(O)C₁-C₆alkyl;

The present invention also includes compounds of Formula XI and FormulaXII:

or a pharmaceutically acceptable salt thereof;

wherein

-   -   R^(12a) and R^(12b) are oxygen protecting groups and at least        one of R^(12a) and R^(12b) is —C(O)OC₁₋₆alkyl, for example        —C(O)OtBu, or —C(O)O-benzyl wherein the alkyl and benzyl group        can be optionally substituted with a substituent selected from        alkoxy, hydroxy, nitro, bromo, chloro, fluoro, azido, and        haloalkyl.

In one embodiment, R^(12a) is —C(O)OC₁₋₆alkyl or —C(O)O-benzyl andR^(12b) is an oxygen protecting group which when attached to the oxygenis an ester, ether, or silyl ether moiety. In an alternative embodiment,R^(12b) is —C(O)OC₁₋₆alkyl or —C(O)O-benzyl and R^(12a) is an oxygenprotecting group which when attached to the oxygen is an ester, ether,or silyl ether moiety. In one embodiment, R^(12a) and R^(12b) are both—C(O)OC₁₋₆alkyl, for example —C(O)OtBu. In one embodiment, R^(12a) andR^(12b) are both —C(O)O-benzyl.

In one embodiment, a compound of Formula XII is Formula XIIA:

In one embodiment, a compound of Formula XII is Formula XIIB:

For example, the protecting group that when attached to the oxygen canbe an ester moiety, for example benzoate acetate. In one embodiment, theoxygen protecting group that when attached to the oxygen is a silylether moiety (for example (trimethylsilyl (TMS), triisopropylsilyl(TIPS), tert-butyldimethylsilyl (TBDMS or TBS) ortert-butyldiphenylsilyl (TBDPS). In one embodiment, the oxygenprotecting group that when attached to the oxygen is an ether moiety,for example methyl ether, methoxymethyl ether, or benzyl ether. Theseprotecting groups can be installed according to one of the proceduresdescribed in Theodora W. Green, Protective Groups in Organic Synthesis,Third Edition, John Wiley & Sons (1999), which is incorporated byreference, for the protection of hydroxyls. For example, when the oxygenprotecting group which when attached to the oxygen is an ester moiety,the compound of Formula XI or Formula XII can be prepared according tothe conditions described in the text on page 149-178 and when the oxygenprotecting group is a silyl ether moiety when attached to the oxygen,the compound of Formula XI or Formula XII can be prepared according tothe conditions described in the text on page 113-147. In one embodiment,the protecting group is a tert-butyldimethylsilyl (TBS) group. The TBSgroup is selectively installed on the primary alcohol over the secondaryalcohol using the conditions described in the text on page 128 and inOgilvie et al. Can. J. Chem. 1979, 57, 2230. These conditions includethe use of TBSCl, DMAP, and NEt₃ in DMF at 25° C.

Non-limiting examples of additional protecting groups which whenattached to the oxygen also include bromobenzoate,p-methoxybenzyloxymethyl ether (MPBM), o-nitrobenzyloxymethyl ether(NBOM), p-nitrobenzyloxymethyl ether, t-butoxymethyl ether,2,2,2-trichloroethoxymethyl ether, 3-bromotetrahydropyranyl ether,tetrahydropyranyl ether, tetrahydrothiopyranyl ether,1-methoxycyclohexyl ether, 1,4-dioxan-2-yl ether, tetrahydrofuranylether, tetrahydrothiofuranyl ether, a substituted phenyl ether,2-picolyl ether, 4-picolyl ether, 1,3-benzodithiolan-2-yl ether,p-chlorophenoxyacetate ester, 3-phenylpropionate ester, p-phenylbenzoateester, alkyl p-nitrophenyl carbonyl, alkyl benzyl carbonyl, alkylp-methoxybenzyl carbonyl, alkyl o-nitrobenzyl carbonyl, and alkylp-nitrobenzyl carbonyl.

Non-limiting examples of R^(12a) and R^(12b) include:

Non-limiting examples of a compound of Formula XI and XII include:

In some embodiments, a compound of Formula I, Formula II, Formula III,Formula IV, Formula V, Formula VI, Formula VII, Formula IX, Formula X,or Formula XIII, for example Compound 1A, Compound 1B, Compound 2A,Compound 2B, Compound 3A, Compound 3B, Compound 4A, or Compound 4B isused in a form at least 90% free of the opposite phosphorus enantiomer,and can be at least 98%, 99% or even 100% free of the oppositephosphorus enantiomer.

Compound 1(Isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate)was previously described in U.S. Pat. Nos. 9,828,410; 10,000,523;10,005,811; 10,239,911; 10,815,266; 10,870,672; 10,870,673; 10,875,885;and, 10,874,687; U.S. applications US 2019-0201433 and US 2020-0222442;and, PCT Applications WO 2016/144918; WO 2018/048937; WO 2019/200005;and, WO 2020/117966 assigned to Atea Pharmaceuticals. The synthesis ofCompound 1 is described in Example 1 below.

Compound 2 was previously disclosed in U.S. Pat. Nos. 10,519,186;10,906,928; 10,894,804; and, 10,874,687 and PCT Applications WO2018/144640; WO 2019/200005; and, WO 2020/117966 assigned to AteaPharmaceuticals. Compound 2A has demonstrated potent in vitro activityagainst clinical isolates of hepatitis C virus (HCV) by inhibiting theRNA-dependent RNA polymerase (RdRp) (Good, S. S. et al. PLoS ONE 15(1),e0227104 (2020)). Compound 2A has been evaluated in a Phase 1b study(Berliba, E. et al. Antimicrob. Agents Chemther. 63, e011201-19 (2020))and a Phase 2 clinical trial (Mungar, Q. et al. EASL abstract (2020)).In the latter study, Compound 2A was safe and well-tolerated for up to12 weeks in HCV-infected subjects and achieved a high rate of efficacy.

The synthesis of Compound 2 (the hemi-sulfate salt ofisopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate)is described in Example 1 below.

In one embodiment Compound 2 is provided in a pharmaceuticallyacceptable composition or solid dosage form thereof.

A non-limiting illustrative process for the preparation of Compound 2includes

-   -   (i) a first step of dissolving Compound 1 in an organic solvent,        for example, acetone, ethyl acetate, methanol, acetonitrile, or        ether, or the like, in a flask or container;    -   (ii) charging a second flask or container with a second organic        solvent, which may be the same as or different from the organic        solvent in step (i), optionally cooling the second solvent to        0-10 degrees C., and adding dropwise H₂SO₄ to the second organic        solvent to create a H₂SO₄/organic solvent mixture; and wherein        the solvent for example may be methanol;    -   (iii) adding dropwise the H₂SO₄/solvent mixture at a molar ratio        of 0.5/1.0 from step (ii) to the solution of Compound 1 of        step (i) at ambient or slightly increased or decreased        temperature (for example 23-35 degrees C.);    -   (iv) stirring the reaction of step (iii) until precipitate of        Compound 2 is formed, for example at ambient or slightly        increased or decreased temperature;    -   (v) optionally filtering the resulting precipitate from        step (iv) and washing with an organic solvent; and    -   (vi) optionally drying the resulting Compound 2 in a vacuum,        optionally at elevated a temperature, for example, 55, 56, 57,        58, 59, or 60° C.

In one embodiment, the solvent of step (iii) is an alcohol, for examplemethanol, ethanol, or isopropyl alcohol. In one embodiment, the solventof step (iii) is an alkyl ester, for example ethyl acetate.

Scheme 1 provides the metabolic pathway of a compound of Formula I,which involves the initial de-esterification of the phosphoramidate(Compound 1) to form metabolite 1-1, which spontaneously decomposes tometabolite 1-2. Metabolite 1-2 is next converted to theN⁶-methyl-2,6-diaminopurine-5′-monophosphate derivative (metabolite1-3), which is in turn metabolized to the free5′-hydroxyl-N⁶-methyl-2,6-diaminopurine nucleoside (metabolite 1-8) and((2R,3R,4R,5R)-5-(2-amino-6-oxo-1,6-dihydro-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2-yl)methyldihydrogen phosphate as the 5′-monophosphate (metabolite 1-4).Metabolite 1-4 is anabolized to the corresponding diphosphate(metabolite 1-5) and then the active triphosphate derivative (metabolite1-6). The 5′-triphosphate can be further metabolized to generate2-amino-9-((2R,3R,4R,5R)-3-fluoro-4-hydroxy-5-(hydroxymethyl)-3-methyltetrahydrofuran-2-yl)-1,9-dihydro-6H-purin-6-one(1-7). Metabolite 1-7 is measurable in plasma and is therefore asurrogate for the active triphosphate (1-6), which is not measurable inplasma.

Definitions

A “patient” or “host” or “subject” is a human or non-human animal inneed of treatment or prevention of COVID-19 caused by the SARS-CoV-2virus. Typically, the host is a human. A “patient” or “host” or“subject” also refers to, for example, a mammal, primate (e.g., human),cow, sheep, goat, horse, dog, cat, rabbit, rat, mice, bird, bat and thelike.

The term “prophylactic” or “preventative” when used refers to theadministration of an active compound to prevent, reduce the likelihoodof an occurrence or a reoccurrence of COVID-19, or to minimize a newinfection relative to infection that would occur without such treatment.The present invention includes both treatment and prophylactic orpreventative therapies. In one embodiment, the active compound isadministered to a host who has been exposed to and is thus at risk ofcontracting COVID-19. In another alternative embodiment, a method toprevent transmission is provided that includes administering aneffective amount of one of the compounds described herein to humans fora sufficient length of time prior to exposure to crowds that can beinfected, including during travel or public events or meetings,including for example, up to 3, 5, 7, 10, 12, 14 or more days prior to acommunicable situation.

The terms “coadminister,” “coadministration,” or “in combination” areused to describe the administration of a compound of Formula I, FormulaII, Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof, according to the present invention incombination with at least one other antiviral active agent. The timingof the coadministration is best determined by the medical specialisttreating the patient. It is sometimes desired that the agents beadministered at the same time. Alternatively, the drugs selected forcombination therapy may be administered at different times to thepatient. Of course, when more than one viral or other infection or othercondition is present, the present compounds may be combined with otheragents to treat that other infection or condition as required.

A “pharmaceutically acceptable salt” is a derivative of the disclosedcompound in which the parent compound is modified to an inorganic andorganic, acid or base addition salt thereof without undue toxicity. Thesalts of the present compounds can be synthesized from the parentcompound with a basic or acidic moiety by conventional chemical methods.Generally, such salts can be prepared by reacting free acid forms ofthese compounds with a stoichiometric amount of the appropriate base(such as Na, Ca, Mg, or K hydroxide, carbonate, bicarbonate, or thelike), or by reacting free base forms of these compounds with astoichiometric amount of the appropriate acid. Such reactions aretypically carried out in water or in an organic solvent, or in a mixtureof the two. Generally, non-aqueous media like ether, ethyl acetate,ethanol, isopropanol, or acetonitrile are typical, where practicable.Salts of the present compounds may optionally be provided in the form ofa solvate.

Examples of pharmaceutically acceptable salts include, but are notlimited to, mineral or organic acid salts of basic residues such asamines; alkali or organic salts of acidic residues such as carboxylicacids; and the like. The pharmaceutically acceptable salts include theconventional salts and the quaternary ammonium salts of the parentcompound formed, for example, from inorganic or organic acids that arenot unduly toxic. For example, acid salts include those derived frominorganic acids such as hydrochloric, hydrobromic, sulfuric, sulfamic,phosphoric, nitric and the like; and the salts prepared from organicacids such as acetic, propionic, succinic, glycolic, stearic, lactic,malic, tartaric, citric, ascorbic, pamoic, maleic, hydroxymaleic,phenylacetic, glutamic, benzoic, salicylic, mesylic, esylic, besylic,sulfanilic, 2-acetoxybenzoic, fumaric, toluenesulfonic, methanesulfonic,ethane disulfonic, oxalic, isethionic, HOOC—(CH2)n-COOH where n is 0-4,and the like, or using a different acid that produces the samecounterion. Lists of additional suitable salts may be found, e.g., inRemington's Pharmaceutical Sciences, 17th ed., Mack Publishing Company,Easton, Pa., p. 1418 (1985).

The compound can be delivered in any molar ratio of salt that deliversthe desired result. For example, the compound can be provided with lessthan a molar equivalent of a counter ion, such as in the form of ahemi-sulfate salt. Alternatively, the compound can be provided with morethan a molar equivalent of counter ion, such as in the form of adi-sulfate salt. Non-limiting examples of molar ratios of the compoundto the counter ion include 1:0.25, 1:0.5, 1:1, and 1:2.

“Alkyl” is a straight chain or branched saturated aliphatic hydrocarbongroup. In certain embodiments, the alkyl is C₁-C₂, C₁-C₃, C₁-C₄, C₁-C₅,or C₁-C₆ (i.e., the alkyl chain can be 1, 2, 3, 4, 5, or 6 carbons inlength). The specified ranges as used herein indicate an alkyl groupwith length of each member of the range described as an independentspecies. For example, C₁-C₆ alkyl as used herein indicates an alkylgroup having from 1, 2, 3, 4, 5, or 6 carbon atoms and is intended tomean that each of these is described as an independent species andC₁-C₄alkyl as used herein indicates an alkyl group having from 1, 2, 3,or 4 carbon atoms and is intended to mean that each of these isdescribed as an independent species. Examples of alkyl include, but arenot limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, t-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl,n-hexyl, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane and2,3-dimethylbutane.

“Cycloalkyl” is a saturated mono-cycle hydrocarbon ring system.Non-limiting examples of cycloalkyl groups include cyclopropyl,cyclobutyl, cyclopentyl, and cyclohexyl.

“Alkenyl” refers to a non-aromatic hydrocarbon group which contains atleast one double bond between adjacent carbon atoms and a similarstructure to an alkyl group as otherwise described herein. For example,an alkenyl group can have to 4 carbon atoms (i.e., C₂-C₄ alkenyl).Examples of suitable alkenyl groups include, but are not limited to,ethenyl or vinyl (—CH═CH₂), allyl (—CH₂CH═CH₂), 1-butenyl (—C═CH—CH₂CH₃)and 2-butenyl (—CH₂CH═CHCH₂).

The term “alkynyl” refers to a non-aromatic hydrocarbon group containingat least one triple bond between adjacent carbon atoms and a similarstructure to an alkyl group as otherwise described herein. For example,an alkynyl group can have 2 to 4 carbon atoms (i.e., C₂-C₄ alkynyl).Examples of alkynyl groups include, but are not limited to ethynyl andpropargyl.

“Aryl” indicates aromatic groups containing only carbon in the aromaticring or rings. In one embodiment, the aryl groups contain 1 to 3separate or fused rings and is 6 to about 14 or 18 ring atoms, withoutheteroatoms as ring members. Aryl groups include, for example, phenyland naphthyl, including 1-naphthyl and 2-naphthyl. In one embodiment,aryl groups are pendant. An example of a pendant ring is a phenyl groupsubstituted with a phenyl group. In one embodiment, the aryl group isoptionally substituted as described above. In one embodiment, arylgroups include, for example, dihydroindole, dihydrobenzofuran,isoindoline-1-one and indolin-2-one.

“Aryl(alkyl)-” is an alkyl group as described herein substituted with anaryl group as described herein. For example, aryl(CH₂)— is benzyl.Examples of aryl(alkyl)- include benzyl, 2-phenyl(alkyl),3-phenyl(alkyl), and napthyl(alkyl).

“Heteroaryl” refers to a stable monocyclic, bicyclic, or multicyclicaromatic ring which contains from 1 to 3, or in some embodiments from 1,2, or 3 heteroatoms selected from N, O, S, B, and P (and typicallyselected from N, O, and S) with remaining ring atoms being carbon, or astable bicyclic or tricyclic system containing at least one 5, 6, or 7membered aromatic ring which contains from 1 to 3, or in someembodiments from 1 to 2, heteroatoms selected from N, O, S, B or P withremaining ring atoms being carbon. In one embodiment, the onlyheteroatom is nitrogen. In one embodiment, the only heteroatom isoxygen. In one embodiment, the only heteroatom is sulfur. Monocyclicheteroaryl groups typically have from 5 or 6 ring atoms. When the totalnumber of S and O atoms in the heteroaryl group exceeds 1, theseheteroatoms are not adjacent to one another. Examples of heteroarylgroups include, but are not limited to, pyridinyl (including, forexample, 2-hydroxypyridinyl), imidazolyl, imidazopyridinyl, pyrimidinyl(including, for example, 4-hydroxypyrimidinyl), pyrazolyl, triazolyl,pyrazinyl, furyl, thienyl, isoxazolyl, thiazolyl, oxadiazolyl, oxazolyl,isothiazolyl, pyrrolyl, quinolinyl, isoquinolinyl,tetrahydroisoquinolinyl, indolyl, benzimidazolyl, benzofuranyl,cinnolinyl, indazolyl, indolizinyl, phthalazinyl, pyridazinyl,triazinyl, isoindolyl, pteridinyl, purinyl, oxadiazolyl, triazolyl,thiadiazolyl, thiadiazolyl, furazanyl, benzofurazanyl, benzothiophenyl,benzothiazolyl, benzoxazolyl, quinazolinyl, quinoxalinyl,naphthyridinyl, tetrahydrofuranyl, and furopyridinyl.

The term “heteroalkyl” refers to an alkyl, alkenyl, alkynyl, orhaloalkyl moiety as defined herein wherein a CH₂ group is eitherreplaced by a heteroatom or a carbon atom is substituted with aheteroatom for example, an amine, carbonyl, carboxy, oxo, thio,phosphate, phosphonate, nitrogen, phosphorus, silicon, or boron. In oneembodiment, the only heteroatom is nitrogen. In one embodiment, the onlyheteroatom is oxygen. In one embodiment, the only heteroatom is sulfur.In one embodiment, “heteroalkyl” is used to indicate a heteroaliphaticgroup (cyclic, acyclic, substituted, unsubstituted, branched orunbranched) having 1-6 carbon atoms.

The term phosphoramidate is used throughout the specification todescribe a moiety at the 5′ position of the furanose ring of thenucleoside and forms a prodrug form of the nucleoside compound, whereinthe phosphorus atom is linked through a 5′-O— bond and wherein thephosphorus is also covalently bound to at least one nitrogen, forming aP—N bond. In some embodiments, the phosphorus is covalently linked tothe amino moiety of a natural or synthetic amino acid (which may be inthe form of an ester). Phosphoramidate groups for use in the presentinvention include, for example, those of the structures:

Other phosphoramidates for use in the present invention include those ofthe structure:

wherein:

-   -   R^(P1) is an optionally substituted linear, branched, or cyclic        alkyl group, or an optionally substituted aryl, heteroaryl or        heterocyclic group or a linked combination thereof, and    -   R^(P2) is a —NR^(N1)R^(N2) group or a B′ group;    -   wherein:    -   R^(N1) and R^(N2) are each independently H, C₁₋₈alkyl,        (C₃-C₇cycloalkyl)C₀-C₄alkyl-, (aryl)C₀-C₄alkyl-,        (C₃-C₆heterocyclo)C₀-C₄alkyl-, or (heteroaryl)C₀-C₄alky-; which        may be optionally substituted; or    -   R^(N1) and R^(N2) along with the nitrogen atom to which that are        attached, join to form a 3 to 7 membered heterocyclic ring;    -   B′ is a

-   -    group;    -   wherein:    -   R¹³ is hydrogen, (C₁-C₈)alkyl, (C₂-C₈)alkenyl, (C₂-C₈)alkynyl,        (C₃-C₈cycloalkyl)C₀-C₄alkyl-, (aryl)C₀-C₄alkyl-,        (C₃-C₆heterocyclo)C₀-C₄alkyl-, (heteroaryl)C₀-C₄alky-, or the        sidechain of an amino acid, for example a sidechain of an amino        acid (as otherwise described herein) often selected from the        group consisting of alanine, β-alanine, arginine, asparagine,        aspartic acid, cysteine, cystine, glutamic acid, glutamine,        glycine, phenylalanine, histidine, isoleucine, lysine, leucine,        methionine, proline, serine, threonine, valine, tryptophan, or        tyrosine (often R¹³ is hydrogen, methyl, isopropyl, or        isobutyl);    -   R¹⁴ is hydrogen, (C₁-C₈)alkyl, (C₂-C₈)alkenyl, (C₂-C₈)alkynyl,        (C₃-C₈cycloalkyl)C₀-C₄alkyl-, (aryl)C₀-C₄alkyl-,        (C₃-C₆heterocyclo)C₀-C₄alkyl-, (heteroaryl)C₀-C₄alky-, or the        sidechain of an amino acid, for example a sidechain of an amino        acid (as otherwise described herein) often selected from the        group consisting of alanine, β-alanine, arginine, asparagine,        aspartic acid, cysteine, cystine, glutamic acid, glutamine,        glycine, phenylalanine, histidine, isoleucine, lysine, leucine,        methionine, proline, serine, threonine, valine, tryptophan, or        tyrosine (often R¹⁴ is hydrogen, methyl, isopropyl, or        isobutyl);    -   R¹⁵ is hydrogen or C₁-C₃alkyl; or    -   R¹³ and R¹⁴ can form a (C₃-C₇)cycloalkyl or (C₃-C₇)heterocyclic        group; or    -   R¹³ and R¹⁴ or R¹⁶ can form (C₃-C₆)heterocyclic group; and    -   R¹⁶ is hydrogen, (C₁-C₆)alkyl, (C₃-C₆)alkenyl, (C₃-C₆)alkynyl,        (C₃-C₈cycloalkyl)C₀-C₄alkyl, (aryl)C₀-C₄alkyl-,        (C₃-C₆heterocyclo)C₀-C₄alkyl-, (heteroaryl)C₀-C₄alky-.

Preferred R^(P1) groups include optionally substituted phenyl, naphthyl,and monocyclic heteroaryl groups, especially those groups (particularlylipophilic groups) which enhance bioavailability of the compounds in thecells of the patient and which exhibit reduced toxicity, enhancedtherapeutic index and enhanced pharmacokinetics (the compounds aremetabolized and excreted more slowly).

Stabilized Phosphate Prodrugs

Stabilized phosphate prodrugs are moieties that can deliver a mono, di,or triphosphate in vivo. For example, McGuigan has disclosedphosphoramidates in U.S. Pat. Nos. 8,933,053; 8,759,318; 8,658,616;8,263,575; 8,119,779; 7,951,787 and 7,115,590. Alios has disclosedthiophosphoramidates in U.S. Pat. Nos. 8,895,723 and 8,871,737incorporated by reference herein. Alios has also disclosed cyclicnucleotides in U.S. Pat. No. 8,772,474 incorporated by reference herein.Idenix has disclosed cyclic phosphoramidates and phosphoramidate/SATEderivatives in WO 2013/177219 incorporated by reference herein. Idenixhas also disclosed substituted carbonyloxymethylphosphoramidatecompounds in WO 2013/039920 incorporated by reference herein. Hostetlerhas disclosed lipid phosphate prodrugs, see, for example, U.S. Pat. No.7,517,858. Hostetler has also disclosed lipid conjugates of phosphonateprodrugs, see, for example, U.S. Pat. Nos. 8,889,658; 8,846,643;8,710,030; 8,309,565; 8,008,308; and 7,790,703. Emory University hasdisclosed nucleotide sphingoid and lipid derivatives in WO 2014/124430.RFS Pharma has disclosed purine nucleoside monophosphate prodrugs in WO2010/091386. Cocrystal Pharma Inc. has also disclosed purine nucleosidemonophosphate prodrugs in U.S. Pat. No. 9,173,893 incorporated byreference herein. HepDirect™ technology is disclosed in the article“Design, Synthesis, and Characterization of a Series of CytochromeP(450) 3A-Activated Prodrugs (HepDirect Prodrugs) Useful for TargetingPhosph(on)ate-Based Drugs to the Liver,” (J. Am. Chem. Soc. 126,5154-5163 (2004). Additional phosphate prodrugs include, but are notlimited to phosphate esters, 3′,5′-cyclic phosphates including CycloSAL,SATE derivatives (S-acyl-2thioesters) and DTE (dithiodiethyl) prodrugs.For literature reviews that disclose non-limiting examples see: A. Rayand K. Hostetler, “Application of kinase bypass strategies to nucleosideantivirals,” Antiviral Research (2011) 277-291; M. Sofia, “Nucleotideprodrugs for HCV therapy,” Antiviral Chemistry and Chemotherapy 2011;22-23-49; and S. Peyrottes et al., “SATE Pronucleotide Approaches: AnOverview,” Mini Reviews in Medicinal Chemistry 2004, 4, 395. In oneembodiment, a 5′-prodrug described in any of these patent filings orliterature can be used in the R^(10A) position of the presentedcompounds.

In one alternative embodiment, the stabilized phosphate prodrugs,include, but are not limited to those described in U.S. Pat. Nos.9,173,893 and 8,609,627, incorporated by reference herein, including forprocesses of preparation. For example, 5′-prodrugs can be represented bythe group:

wherein

-   -   Z is O or S;    -   R¹⁷ and R¹⁸, when administered in vivo, are capable of providing        the nucleoside monophosphate, diphosphate, or triphosphate.        Representative R¹² and R¹³ are independently selected from:    -   (a) OR¹⁹ where R¹⁹ is selected from H, Li, Na, K, phenyl and        pyridinyl and wherein phenyl and pyridinyl are optionally        substituted with one to three substituents independently        selected from the group consisting of (CH₂)₀₋₆CO₂R²⁰ and        (CH₂)₀₋₆CON(R²⁰)₂;    -   R²⁰ is independently H, C₁₋₂₀ alkyl, the carbon chain derived        from a fatty alcohol (such as oleyl alcohol, octacosanol,        triacontanol, linoleyl alcohol, and etc) or C₁₋₂₀ alkyl        substituted with a lower alkyl, alkoxy, di(lower alkyl)-amino,        fluoro, C₃₋₁₀ cycloalkyl, cycloalkyl alkyl, cycloheteroalkyl,        aryl, such as phenyl, heteroaryl, such as, pyridinyl,        substituted aryl, or substituted heteroaryl; wherein the        substituents are C₁₋₅ alkyl, or C₁₋₅ alkyl substituted with a        lower alkyl, alkoxy, di(lower alkyl)-amino, fluoro, C₃₋₁₀        cycloalkyl, or cycloalkyl;

-   -   (c) the ester of a D-amino acid or L-amino acid:

-   -   wherein    -   R²¹ is restricted to those sidechains occurring in natural        L-amino acids, and    -   R²² is H, C₁₋₂₀ alkyl, the carbon chain derived from a fatty        alcohol (such as oleyl alcohol, octacosanol, triacontanol,        linoleyl alcohol, and etc) or C₁₋₂₀ alkyl substituted with a        lower alkyl, alkoxy, di(lower alkyl)-amino, fluoro, C₃₋₁₀        cycloalkyl, cycloalkyl alkyl, cycloheteroalkyl, aryl, such as        phenyl, heteroaryl, such as, pyridinyl, substituted aryl, or        substituted heteroaryl; wherein the substituents are C₁₋₅ alkyl,        or C₁₋₅ alkyl substituted with a lower alkyl, alkoxy, di(lower        alkyl)-amino, fluoro, C₃₋₁₀ cycloalkyl, or cycloalkyl;    -   (d) R¹⁷ and R¹⁸ can come together to form a ring:

-   -   wherein    -   R²³ is H, C₁₋₂₀ alkyl, C₁₋₂₀ alkenyl, the carbon chain derived        from a fatty alcohol (such as oleyl alcohol, octacosanol,        triacontanol, linoleyl alcohol, etc) or C₁₋₂₀ alkyl substituted        with a lower alkyl, alkoxy, di(lower alkyl)-amino, fluoro, C₃₋₁₀        cycloalkyl, cycloalkyl alkyl, cycloheteroalkyl, aryl, such as        phenyl, heteroaryl, such as, pyridinyl, substituted aryl, or        substituted heteroaryl; wherein the substituents are C₁₋₅ alkyl,        or C₁₋₅ alkyl substituted with a lower alkyl, alkoxy, di(lower        alkyl)-amino, fluoro, C₃₋₁₀ cycloalkyl, or cycloalkyl;    -   (e) R¹⁷ and R⁸ can come together to form a ring selected from

-   -   wherein    -   R²⁴ is selected from H, C₁₋₂₀ alkyl, C₁₋₂₀ alkenyl, the carbon        chain derived from a fatty acid (such as oleic acid, linoleic        acid, and the like), and C₁₋₂₀ alkyl substituted with a lower        alkyl, alkoxy, di(lower alkyl)-amino, fluoro, C₃₋₁₀ cycloalkyl,        cycloalkyl alkyl, cycloheteroalkyl, aryl, such as phenyl,        heteroaryl, such as pyridinyl, substituted aryl, or substituted        heteroaryl; wherein the substituents are C₁₋₅ alkyl, or C₁₋₅        alkyl substituted with a lower alkyl, alkoxy, di(lower        alkyl)-amino, fluoro, C₃₋₁₀ cycloalkyl, or cycloalkyl; and    -   R²⁵ is O or NH.

In an alternate embodiment, 3′,5′-prodrugs can be represented by:

wherein:

-   -   when chirality exists at the phosphorous center it may be wholly        or partially R_(p) or S_(p) or any mixture thereof, and can be        enantiomerically enriched;    -   R²⁶ is selected from OR¹⁹,

-   -    and fatty alcohol derived (for example but not limited to        linoleyl-O— and oleyl-O—;    -   R¹¹ is selected from R¹ and hydrogen; and    -   R¹, R²¹, R²², and R¹⁹ are as defined herein.        Isotopic Substitution

The present invention includes the use of an effective amount of acompound of Formula I (including for example Compound 1, 1A or 1B),Formula II (including for example, Compound 3, 3A, or 3B), Formula III(including for example, a compound of Formula IIIa, Formula IIIb,Formula IIIc, Formula IIId, Formula IIIe, or Formula IIIf), Formula IV(including for example, a compound of Formula IVa, Formula IVb, FormulaIVc, Formula IVd, Formula IVe, or Formula IVf), Formula V, Formula VI,Formula VII, Formula VIII, Formula IX, Formula X or a pharmaceuticallyacceptable salt thereof, wherein the compounds have a desired isotopicsubstitutions of atoms at amounts above the natural abundance of theisotope, i.e., enriched. Isotopes are atoms having the same atomicnumber but different mass numbers, i.e., the same number of protons buta different number of neutrons. By way of general example and withoutlimitation, isotopes of hydrogen, for example, deuterium (2H) andtritium (³H) may be used anywhere in described structures. Alternativelyor in addition, isotopes of carbon, e.g., ¹³C and ¹⁴C, may be used. Anexample of an isotopic substitution is deuterium for hydrogen at one ormore locations on the molecule to improve the performance of the drug.The deuterium can be bound in a location of bond breakage duringmetabolism (an α-deuterium kinetic isotope effect) or next to or nearthe site of bond breakage (a β-deuterium kinetic isotope effect).Achillion Pharmaceuticals, Inc. (WO/2014/169278 and WO/2014/169280)describes deuteration of nucleotides to improve their pharmacokinetic orpharmacodynamic, including at the 5-position of the molecule.

Substitution with isotopes such as deuterium can afford certaintherapeutic advantages resulting from greater metabolic stability, suchas, for example, increased in vivo half-life or reduced dosagerequirements. Substitution of deuterium for hydrogen at a site ofmetabolic break-down can reduce the rate of or eliminate the metabolismat that bond. At any position of the compound that a hydrogen atom maybe present, the hydrogen atom can be any isotope of hydrogen, includingprotium (H), deuterium (²H) and tritium (3H). Thus, reference herein toa compound encompasses all potential isotopic forms unless the contextclearly dictates otherwise.

The term “isotopically-labeled” analog refers to an analog that is a“deuterated analog”, a “¹³C-labeled analog,” or a“deuterated/¹³C-labeled analog.” The term “deuterated analog” means acompound described herein, whereby a H-isotope, i.e., hydrogen/protium(H), is substituted by a H-isotope, i.e., deuterium (²H). Deuteriumsubstitution can be partial or complete. Partial deuterium substitutionmeans that at least one hydrogen is substituted by at least onedeuterium.

In certain embodiments, the isotope is 90, 95 or 99% or more enriched inan isotope at any location of interest. In some embodiments it isdeuterium that is 90, 95 or 99% enriched at a desired location. Unlessindicated to the contrary, the deuteration is at least 80% at theselected location. Deuteration of the nucleoside can occur at anyreplaceable hydrogen that provides the desired results.

In one embodiment, a compound of Formula XIII or a pharmaceuticallyacceptable salt thereof, optionally in a pharmaceutically carrier, isused to treat or prevent COVID-19 disease caused by SARS-CoV-2 in a hostin need thereof as described herein:

wherein

-   -   R⁶ is selected from hydrogen, —C(O)R^(6A), —C(O)OR^(6A),        C₁₋₆alkyl, and —CH₂—O—R^(6A);    -   R⁶ is selected from hydrogen, —C(O)R^(6A), —C(O)OR^(6A),        C₁₋₆alkyl, and —CH₂—O—R^(6A) and in an alternative embodiment,        —C(O)NR^(6B)R^(6C);    -   R^(6A) is selected from hydrogen, C₁₋₆alkyl, C₁-C₆haloalkyl (for        example, —CHCl₂, —CCl₃, —CH₂Cl, —CF₃, —CHF₂, —CH₂F), aryl, and        aryl(C₁₋₆alkyl)- wherein the aryl group is optionally        substituted with a substituent selected from alkoxy, hydroxy,        nitro, bromo, chloro, fluoro, azido, and haloalkyl and in an        alternative embodiment, R^(6A) is selected from C₁₋₂₀alkyl and        C₂₋₂₀alkenyl;    -   R^(6B) and R^(6C) are independently selected from hydrogen,        C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl, arylalkyl, heteroaryl, and        heteroarylalkyl wherein the C₁₋₂₀alkyl, C₂₋₂₀alkenyl, aryl,        arylalkyl, heteroaryl, and heteroarylalkyl can optionally be        substituted with at least one substituent selected from alkoxy        (including but not limited to methoxy and ethoxy), hydroxy,        nitro, bromo, chloro, fluoro, azido, and haloalkyl;    -   R³⁰ is CH₃, CD₃, CHD₂, or CH₂D;    -   R³¹ is NH₂ or D or in an alternative embodiment, CD₃;    -   R³² is CH₃, CD₃, CHD₂, or CH₂D; and    -   Y is selected from F and Cl; and    -   R¹, R², R³, R^(4a), R^(4b), and R⁵ are as defined herein.

For example, non-limiting examples of compounds of Formula XIII include:

Additional examples of compound of Formula XIII include:

Methods of Treatment or Prophylaxis

Treatment, as used herein, refers to the administration of a compound ofFormula I, Formula II, Formula III, Formula IV, Formula V, Formula VI,Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, in an effective amount to ahost, for example a human, that is or may become infected with theSARS-CoV-2 virus. In one embodiment the method of treatment comprisesadministration of an effective amount of Compound 1A or Compound 3A or apharmaceutically acceptable salt thereof, for example Compound 2A orCompound 4A. In one embodiment the method of treatment comprisesadministration of an effective amount of Compound 1B or Compound 3B or apharmaceutically acceptable salt thereof, for example Compound 2B orCompound 4B.

The present invention also includes prophylactic or preventativetherapies. In one embodiment, a compound of Formula I, Formula II,Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof, is administered to a host who has been exposedto and thus is at risk of infection or at risk of reinfection with theSARS-CoV-2 virus. Prophylactic treatment may be administered, forexample, to a subject not yet exposed to or infected with SARS-CoV-2,but who is susceptible to, or otherwise at risk of exposure or infectionwith COVID-19. In one embodiment, a host at risk for infection orreinfection is administered a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof indefinitely until the risk of exposure no longer exists.

In another alternative embodiment, a method to prevent transmission isprovided that includes administering an effective amount of one of thecompounds described herein to humans for a sufficient length of timeprior to exposure to crowds that can be infected, including duringtravel or public events or meetings, including for example, up to 3, 5,7, 10, 12, 14 or more days prior to a communicable situation, eitherbecause the human is infected or to prevent infection from an infectedperson in the communicable situation.

In one embodiment, a compound of Formula I, Formula II, Formula III,Formula IV, Formula V, Formula VI, Formula VII, Formula VIII, FormulaIX, Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof is administered in an effective amount for at least two weeks,three weeks, one month, two months, three months, four months, fivemonths, or six months or more after infection.

The invention is directed to a method of treatment of COVID-19,including drug resistant and multidrug resistant forms of the virus andrelated disease states, conditions, or complications of the viralinfection, including pneumonia, such as 2019 novel coronavirus-infectedpneumonia (NCIP), acute lung injury (ALI), and acute respiratorydistress syndrome (ARDS). Additional non-limiting complications includehypoxemic respiratory failure, acute respiratory failure (ARF), acuteliver injury, acute cardiac injury, acute kidney injury, septic shock,disseminated intravascular coagulation, blood clots, multisysteminflammatory syndrome, chronic fatigue, rhabdomyolysis, and cytokinestorm.

The method also comprises administering to a host in need thereof,typically a human, an effective amount of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, optionally in combination withat least one additional bioactive agent, for example, an additionalanti-viral agent, further optionally in combination with apharmaceutically acceptable carrier additive and/or excipient.

In one embodiment, the administration of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof to a patient in need thereofresults in a reduction in the incidence of progressive respiratoryinsufficiency (PRI) as measured by greater than or equal to a 1-tier oreven a 2-tier or more increase in respiratory support methods requiredto maintain satisfactory oxygenation (SpO₂≥93%) using the 6-tierhierarchical levels of respiratory support methods described below.

The scale of increasing respiratory support levels includes:

-   -   Level 1: Normal oxygenation on room air (SpO₂≥93%), no need for        supplemental O₂    -   Level 2: Persistent hypoxemia on room air (SpO₂≥93) with        requirement for low-level supplemental O₂ by nasal cannular or        mask (up to 2 L/min) to maintain SpO₂≥93    -   Level 3: Requirement for higher levels of passive supplemental        O₂ by nasal cannular or mask (up to 2 L/min) to maintain SpO₂≥93    -   Level 4: Requirement for oxygenation by positive-pressure        devices, e.g., Continuous Positive Airway Pressure (CPAP) or        Bi-level Positive Airway Pressure (BiPAP) or other non-invasive        positive-pressure respiratory support methods to main        satisfactory oxygenation and/or ventilation    -   Level 5: Requires invasive respiratory support (intubated        mechanical ventilation or ECMO)    -   Level 6: Death

In one embodiment, the reduction in PRI is an increase from level 5 tolevel 3, level 5 to level 2, or level 5 to level 1. In one embodiment,the reduction in PRI is an increase from level 4 to level 2 or level 4to level 1. In one embodiment, the reduction in PRI is an increase fromlevel 3 to level 1.

In one embodiment, the administration of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof reduces the median time toClinical Recovery (status 6, 7, or 8 in the NIAID Clinical Status scaleusing an adapted National Institute of Allergy and Infectious Diseases(NIAID) ordinal scale of Clinical Status) by at least 3, 4, 5, or moredays. In one embodiment, the administration of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof results in an improvement asmeasured by the adapted ordinal scale of Clinical Status.

From most severe disease to progressively less severe disease, thestages of the adapted ordinal scale of overall Clinical Status aredefined as follows:

-   -   1. Death    -   2. Hospitalized, on invasive mechanical ventilation or ECMO    -   3. Hospitalized, on non-invasive ventilation or high flow oxygen        devices    -   4. Hospitalized, requiring supplemental oxygen    -   5. Hospitalized, not requiring supplemental oxygen—requiring        ongoing medical care (COVID-19 related or otherwise)    -   6. Hospitalized, not requiring supplemental oxygen; no longer        requires close medical care for COVID-19    -   7. Not hospitalized, but with limitation on activities and        needing close outpatient care for COVID-19 manifestations    -   8. Not hospitalized, no limitations on activities, no need for        continued close medical care

In one embodiment, the administration of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof reduces the median time toClinical Recovery (status 6, 7, or 8 in the NIAID Clinical Status scaleusing an adapted National Institute of Allergy and Infectious Diseases(NIAID) ordinal scale of Clinical Status) by at least 5 days, at least 6days, at least 7 days, at least 8 days, at least 9 days, or at least 10days.

In one embodiment, the administration of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof reduces the duration ofhospitalization for a patient infected with the SARS-CoV-2 virus.

In one embodiment, the administration of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof reduces the time to sustainednon-detectable SARS-CoV-2 virus in the nose and/or throat in a patientinfected with the SARS-CoV-2 virus.

In one embodiment, the administration of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof reduces respiratory failure ordeath.

In one embodiment, the administration of a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof reduces the proportion ofpatients in a hospital population who are SARS-CoV-2 positive after atleast about 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 days of treatment.

In another embodiment, a method of treating or preventing a SARS-CoV-2infection in a host, typically a human, in need thereof is provided byadministering to the host an effective amount of a compound of FormulaI, Formula II, Formula III, Formula IV, Formula V, Formula VI, FormulaVII, Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, wherein the SARS-CoV-2infection is caused by a viral variant that has developed a natural ordrug-induced mutation over the wild-type.

In some embodiments, the SARS-CoV-2 variant has a natural mutation ordrug-induced mutation in a viral protein selected from an envelope (E)protein, membrane (M) protein, spike (S) protein, nsp1, nsp2, nsp3,nsp4, nsp5, nsp 6, nsp7, nsp8, nsp9, nsp10, nsp12, nsp13, nsp14, nsp15,nsp16, ORF1ab, ORF3a, ORF6, ORF7a, ORF7b, ORF8, and ORF10. In someembodiments, the SARS-CoV-2 variant has a mutation which results in theacquired resistance to one or more anti-viral drugs.

In some embodiments, the SARS-CoV-2 variant has a deletion of the spikeprotein amino acids H69 and V70.

In some embodiments, the SARS-CoV-2 variant has a deletion of the spikeprotein amino acids D614G.

In some embodiments, the SARS-CoV-2 variant has a deletion of the spikeprotein amino acid Y144.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution N501Y.

In some embodiments, the SARS-CoV-2 variant which has a spike proteinamino acid substitution A570D.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution P681H.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution T716I.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution S982A.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution D1118H.

In some embodiments, the SARS-CoV-2 variant has a premature stop codonmutation Q27 stop in the protein product of ORF8.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution K417N.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution E484K.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution K417N.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution D215G.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution A701V.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution L18F.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution R246I.

In some embodiments, the SARS-CoV-2 variant has a spike protein deletionat amino acids 242-244 In some embodiments, the SARS-CoV-2 variant has aspike protein amino acid substitution Y453F.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution I692V.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution M1229I.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution N439K.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution A222V.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution S477N.

In some embodiments, the SARS-CoV-2 variant has a spike protein aminoacid substitution A376T.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution P323L.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution Y455I.

In some embodiments, the SARS-CoV-2 variant has a Orf8 protein aminoacid substitution R52I.

In some embodiments, the SARS-CoV-2 variant has an ORF8 protein aminoacid substitution Y73C.

In some embodiments, the SARS-CoV-2 variant has a nucleoside (N) proteinamino acid substitution D3L.

In some embodiments, the SARS-CoV-2 variant has a nucleoside (N) proteinamino acid substitution S235F.

In some embodiments, the SARS-CoV-2 variant has a ORF1ab protein aminoacid substitution T1001I.

In some embodiments, the SARS-CoV-2 variant has a ORF1ab protein aminoacid substitution A1708D.

In some embodiments, the SARS-CoV-2 variant has a ORF1ab protein aminoacid substitution I2230T.

In some embodiments, the SARS-CoV-2 variant has a ORF1ab protein aminoacid SGF 3675-3677 deletion.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution S861X, wherein X is any amino acid.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution F480V.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution V557L.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution D484Y.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution F480X, wherein X=any amino acid.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution V557X, wherein X=any amino acid.

In some embodiments, the SARS-CoV-2 variant has a nsp12 protein aminoacid substitution D484X, wherein X=any amino acid.

In some embodiments, the SARS-CoV-2 variant includes a deletion of thespike protein amino acids 69-70, deletion of the spike protein aminoacid Y144, the spike protein amino acid substitution N501Y, the spikeprotein amino acid substitution A570D, the spike protein amino acidsubstitution D614G, the spike protein amino acid substitution P681H, thespike protein amino acid substitution T716I, the spike protein aminoacid substitution S982A, the spike protein amino acid substitutionD1118H, and a premature stop codon mutation (Q27stop) in the proteinproduct of ORF8.

In some embodiments, the SARS-CoV-2 variant includes amino acidsubstitutions in the spike protein of N501Y, K417N, E484K, D80A, D215G,L18F, and R246I in the spike protein, and amino acid deletion at aminoacids 242-244 of the spike protein.

In some embodiments, the SARS-CoV-2 variant is selected from SARS-CoV-2clade O, S, L, V, G, GH, or GR as described by Alm et al., “Geographicaland temporal distribution of SARS-CoV-2 clades in the WHO EuropeanRegion, January to June 2020”. Euro Surveillance: Bulletin European Surles Maladies Transmissibles=European Communicable Disease Bulletin. 25(32).

In some embodiments, the SARS-CoV-2 variant is selected from SARS-CoV-2clade G614, S84, V251, I378 or D392 as described by Guan et al., Agenetic barcode of SARS-CoV-2 for monitoring global distribution ofdifferent clades during the COVID-19 pandemic. Int J Infect Dis. 2020November; 100: 216-223.

In some embodiments, the SARS-CoV-2 variant is selected from SARS-CoV-2clade 19A, 19B, 20A, or 20C as described by Nextstrain: Genomicepidemiology of novel coronavirus—Global sub-sampling. Available from:https://nextstrain.org/ncov.

In some embodiments, the SARS-CoV-2 variant is selected from SARS-CoV-2lineage A, B, B.1, B.1.1, or B.1.177 as described by Rambaut et al.,Phylogenetic Assignment of Named Global Outbreak LINeages (pangolin).San Francisco: GitHub. Available from:https://github.com/cov-lineages/pangolin; Rambaut et al. A dynamicnomenclature proposal for SARS-CoV-2 lineages to assist genomicepidemiology. Nat Microbiol. 2020 November; 5(11):1403-1407; Rambaut etal. SARS-CoV-2 lineages. Available from: https://cov-lineages.org/.

In some embodiments, the SARS-CoV-2 variant is the “Cluster 5” variant,which includes the spike protein amino acid substitution D614G.

In some embodiments, the SARS-CoV-2 variant is VUI 202012/01 (VariantUnder Investigation, year 2020, month 12, variant 01) (also known asB.1.1.7 lineage and 20B/501Y.V1), which has been defined by multiplespike protein changes including deletion of the spike protein aminoacids 69-70, deletion of the spike protein amino acid Y144, the spikeprotein amino acid substitution N501Y, the spike protein amino acidsubstitution A570D, the spike protein amino acid substitution D614G, thespike protein amino acid substitution P681H, the spike protein aminoacid substitution T716I, the spike protein amino acid substitutionS982A, the spike protein amino acid substitution D1118H, and a prematurestop codon mutation (Q27stop) in the protein product of ORF8.

In some embodiments, the SARS-CoV-2 variant is the B.1.351 lineagevariant (also known as 501.V2, 20C/501Y.V2), which includes severalmutations in the receptor-binding domain (RBD) in the spike protein:N501Y, K417N, and E484K, which allows the virus to attach more easily tohuman cells, as well as amino acid substitution D80A in the spikeprotein, an amino acid substitution D215G in the spike protein, an aminoacid substitution A701V in the spike protein, an amino acid substitutionL18F in the spike protein, an amino acid substitution R246I in the spikeprotein, and amino acid deletion at amino acids 242-244 of the spikeprotein.

In some embodiments, the SARS-CoV-2 variant is the 501Y.V2 lineagevariant (also known as 501Y.V2, 20C/20H/501Y.V2), which also includesthe spike protein mutations N501Y, K417N, and E484K.

In some embodiments, the SARS-CoV-2 variant is the P.1 lineage variant(also known as the Brazil(ian) variant), which includes ten mutations inthe spike protein mutations, including N501Y and E484K.

In some embodiments, the SARS-CoV-2 variant is the B.1.1.207 lineagevariant, which includes a P681H mutation in the spike protein.

In some embodiments, the SARS-CoV-2 variant is the danish mink variantwhich includes an amino acid deletion of H69 and V70 in the spikeprotein, and an amino acid substitution Y453F in the spike protein.

In some embodiments, the SARS-CoV-2 variant is the danish mink cluster 5variant, which includes an amino acid deletion of H69 and V70 in thespike protein, an amino acid substitution Y453F in the spike protein, anamino acid substitution I692V in the spike protein, and an amino acidsubstitution M1229I in the spike protein.

In some embodiments, the SARS-CoV-2 variant includes an amino aciddeletion of H69 and V70 in the spike protein, and an amino acidsubstitution N439K in the spike protein.

In some embodiments, the SARS-CoV-2 variant is the Nexstrain cluster20A.EU1 variant, which includes an amino acid substitution A222V in thespike protein.

In some embodiments, the SARS-CoV-2 variant is the Nexstrain cluster20A.EU2 variant, which includes an amino acid substitution S477N in thespike protein, and an amino acid substitution A376T in the nucleocapsidprotein.

In some embodiments, the SARS-CoV-2 variant has one or more of thefollowing mutations selected from: an amino acid substitution T1001I inthe protein product of ORF1ab; an amino acid substitution A1708D in theprotein product of ORF1a; an amino acid substitution I2230T in theprotein product of ORF1ab; a deletion of amino acids SGF at 3675-3677 inthe protein product of ORF1ab; an amino acid substitution G251V in theprotein product of ORF3a; an amino acid substitution S24L in the proteinproduct of ORF8; an amino acid substitution R52I in the protein productof ORF8; an amino acid substitution Y73C in the protein product of ORF8;an amino acid substitution L84S in the protein product of ORF8; an aminoacid substitution P323L in the nsp12 domain; an amino acid substitutionY455I in the nsp12 domain; an amino acid substitution Q57H in theprotein product of ORF3a; an amino acid substitution R27C in nsp2; anamino acid substitution V198I in nsp2; an amino acid substitution T85Iin nsp2; an amino acid substitution P585S in nsp2; an amino acidsubstitution I559V in nsp2; an amino acid substitution M33I in nsp4; anamino acid substitution G15S in nsp5; an amino acid substitution L37F innsp6; an amino acid substitution Y541C in nsp13; an amino acidsubstitution P504L in nsp13; an amino acid substitution S477N in thespike protein; an amino acid substitution N439K in the spike protein; anamino acid substitution N501Y in the spike protein; an amino acidsubstitution Y453F in the spike protein; an amino acid substitutionK417N in the spike protein; an amino acid substitution E484K in thespike protein; an amino acid substitution A222V in the spike protein; anamino acid substitution S98F in the spike protein; an amino acidsubstitution D80Y in the spike protein; an amino acid substitution A626Sin the spike protein; an amino acid substitution V1122L in the spikeprotein; an amino acid substitution A570D in the spike protein; an aminoacid substitution P681H in the spike protein; an amino acid substitutionVI 122L in the spike protein; an amino acid substitution T716I in thespike protein; an amino acid substitution S982A in the spike protein; anamino acid substitution D1118H in the spike protein; an amino acidsubstitution E583D in the spike protein; an amino acid substitutionV483A in the spike protein; an amino acid substitution Q675R in thespike protein; an amino acid substitution A344S in the spike protein; anamino acid substitution T345S in the spike protein; an amino acidsubstitution R346K in the spike protein; an amino acid substitutionA348S in the spike protein; an amino acid substitution A348T in thespike protein; an amino acid substitution N354K in the spike protein; anamino acid substitution S359N in the spike protein; an amino acidsubstitution V367F in the spike protein; an amino acid substitutionV382L in the spike protein; an amino acid substitution P384L in thespike protein; an amino acid substitution P384S in the spike protein; anamino acid substitution T385S in the spike protein; an amino acidsubstitution V395I in the spike protein; an amino acid substitutionR403K in the spike protein; an amino acid substitution D405V in thespike protein; an amino acid substitution Q414P in the spike protein; anamino acid substitution Q414E in the spike protein; an amino acidsubstitution I418V in the spike protein; an amino acid substitutionL441I in the spike protein; an amino acid substitution R457K in thespike protein; an amino acid substitution K458Q in the spike protein; anamino acid substitution P463S in the spike protein; an amino acidsubstitution A475V in the spike protein; an amino acid substitutionG476S in the spike protein; an amino acid substitution T478A in thespike protein; an amino acid substitution P479L in the spike protein; anamino acid substitution V483A in the spike protein; an amino acidsubstitution F490L in the spike protein; an amino acid substitutionQ493L in the spike protein; an amino acid substitution A520S in thespike protein; an amino acid substitution L5F in the spike protein; anamino acid substitution P521R in the spike protein; an amino acidsubstitution A522S in the spike protein; an amino acid substitutionA831V in the spike protein; an amino acid substitution D839Y in thespike protein; an amino acid substitution D839N in the spike protein; anamino acid substitution D839E in the spike protein; an amino acidsubstitution L8V in the spike protein; an amino acid substitution L8W inthe spike protein; an amino acid substitution H49Y in the spike protein;a deletion of amino acid H69 in the spike protein; a deletion of aminoacid V70 in the spike protein; a deletion of amino acid Y144 in thespike protein; an amino acid substitution D3L in the nucleocapsidprotein; an amino acid substitution S253F in the nucleocapsid protein;an amino acid substitution RG203KR in the nucleocapsid protein; an aminoacid substitution G214C in the nucleocapsid protein; an amino acidsubstitution S194L in the nucleocapsid protein; an amino acidsubstitution F377L in the nsp14 protein; an amino acid substitutionK1186R in nsp3; or an amino acid substitution A58T in nsp3.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the envelope (E) protein: S68F; L73F; P71L; S55F;R69I; T9I; V24M; D72H; T30I; S68C; V75L; V58F; V75F; or L21F; andcombinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the membrane (M) protein: T175M; D3G; V23L; W31C;A2V; V70F; W75L; M109I; I52T; L46F; V70I; D3Y; K162N; H125Y; K15R;D209Y; R146H; R158C; L87F; A2S; A69S; S214I; T208I; L124F; or S4F; andcombinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nucleocapsid (N) protein: RG203KR; S194L;S197L; P13L; D103Y; S1931; S188L; I292T; S202N; D401Y; S190I; D22G;A208G; T205I; S183Y; S33I; D81Y; T393I; A119S; D377Y; S37P; T247I;A156S; D128Y; P199L; R195I; P207L; E62V; R209T; T362I; G18C; T24N;R185C; S180I; M234I; Q9H; P383L; A35S; P383S; D348H; K374N; R32H; S327L;G179C; G238C; A55S; S190G; H300Y; A119V; D144Y; L139F; P199S; P344S;P6L; R203K; P364L; R209I; S188P; A35V; K387N; P122L; R191C; R195K;T391I; A252S; Q418L; T271I; T325I; G18V; L161F; Q289H; R203S; P162L;D340N; K373N; P168Q; A211V; D3L; G212V; K370N; P151L; T334I; A359S;G34W; P67T; R203M; D144N; R191L; S232I; D402Y; P168S; S187L; T366I;A152S; A381T; N140T; T198I; A251V; A398V; A90S; D348Y; D377G; G204R;G243C; G34E; Q229H; R185L; T24I; T379I; A134V; N196I; P365S; Q384H;R276I; S235F; D216A; M210I; M322I; P20S; Q389H; R209 deletion; or V246I;and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp1 protein: M85; D75E; G82 deletion; V84deletion; P80 deletion; H83 deletion; V86 deletion; H81 deletion; E87deletion; L88 deletion; K141 deletion; A79 deletion; V89 deletion; V56I;R124C; D75G; A90 deletion; Y118C; D139N; Y136 deletion; G30D; R24C;D139Y; E37K; H45Y; H110Y; G52S; I71V; D156 deletion; A76T; E37D; S135deletion; S166G; A138T; F157 deletion; G49C; M85I; or D144A; andcombinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp10 protein: D64E; P136S; A104V; A32V;T121; T111I; P84S; T511; I55V; T102I; or T51A; and combinations thereof.

In some embodiments, the SARS-CoV2 variant contains one or more of thefollowing mutations in the nsp12 protein: P323L; T141I; A449V; S434F;M666I; H613Y; S647I; M380I; E922D; M629I; G774S; M601I; E436G; N491S;Q822H; A443V; T85I; A423V; M463I; T26I; A656T; M668I; T806I; T276M;T801N; V588L; K267N; V880I; K718R; L514F; F415S; T252N; Y38H; E744D;H752Q; I171V; S913L; A526V; A382V; G228C; P94L; E84K; K59N; P830S;T908I; P21S; D879Y; G108D; K780N; R279S; D258Y; T259I; K263N; D284Y;Q292H; T293I; N297S; V299F; D304Y; T319I; F321L; P328S; V330E; I333T;G337C; T344I; Y346H; L351P; V354L; Q357H; E370G; L372F; A400S; T402I;V405F; V410I; D418N; K426N; K430N; V435F; Q444H; D445G; A448V; R457C;P461T; C464F; I466V; V473F; K478N; D481G; D517G; D523N; A529V; P537S;S549N; A555V; C563F; M566I; A581T; G584V; A585T; G596S; T604I; S607I;D608G; V609I; M615V; W617L; M629V; I632V; L636F; L638F; A639V; T643I;T644M; L648F; V667I; A699S; N713S; H725; N734T; D736N; V737F; T739I;V742M; N743S; M756I; L7581; A771V; L775V; A777T; K780T; F793L; T8011;T803A; H810Y; G823C; D825Y; V827A; Y828H; V848L; T870I; K871R; N874D;Q875R; E876D; H882Y; H892Y; D901Y; M906I; N909D; T912N; P918S; E919D;A923T; F480V; V557L; D484Y; or S433G; and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp13 protein: Y541C; P504L; A18V; R392C;P47L; S485L; L297P; H290Y; T127I; L176F; V193I; V570L; D260Y; V49I;Q518H; S468L; A598V; D204Y; S74L; T588I; G206C; V226L; V348L; M576I;A302D; P53S; T481M; K524N; A338V; P419S; V479F; P77L; V169F; N124S;P78S; S80G; V496L; A4V; T413I; A296S; A368S; K460R; L297F; P172S; A302S;P402S; T530I; L428F; P504S; A368V; D458Y; P364S; S74P; T416A; A568V;M474I; S166L; S350L; D344N; E341D; I432T; L581F; S38L; T250I; Y253H;A509V; E244D; H164Y; S74A; T141I; V356F; E319D; E365D; G170S; L526F;R155C; or Y396C; and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp14 protein: A320V; F233L; T250I; V182L;A225V; R289C; A274S; P24L; I150T; S374A; H26Y; L177F; L157F; T16I;A482V; P297S; V120A; S255I; P203L; A23 deletion; K311N; M72I; V290F;F431L; K349N; M58I; P140S; R205C; T193A; L409F; P443S; Y260C; D345G;E204D; R163C; R81K; T524I; T113I; T31I; L493F; A119V; D345Y; M501I;A360V; A371V; T206I; V287F; A360S; I74T; M315I; P142L; or Q343K; andcombinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp15 protein: V320L; A217V; V22L; V172L;D219N; P205S; V127F; Q19H; M218 deletion; A92V; D282G; I252V; T33I;G129S; L331F; A81V; V69L; S312F; T325I; A171V; R206S; D272Y; D87N;S288F; K109R; P270S; P65S; D267Y; D128Y; E2151; T144I; S261L; S287L;T112I; E260K; P205L; S161I; V66L; D39Y; or T114A; or combinationsthereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp16 protein: S33R; K160R; P134S; Q28K;T195I; V78G; T35I; G265V; K249N; A204S; K182N; R287I; A188S; A116V;T140I; L111F; M270T; R216N; A188V; A34V; D108N; L163F; L163H; M17I;T91M; A226S; G77R; L126F; N298L; R216S; T481; Q238H; or R279K; andcombinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp2 protein: T85I P585S; I559V; D268; G212D;V198I; H237R; F10L; G339S; T166I; R27C; L271F; S211F; P91S; G199E;T371I; A336V; I120F; S122F; A476V; S138L; V480A; T388I; T634I; P129S;R218C; I188T; T170I; P568L; E574A; I367V; H208Y; S99F; T429I; A306V;M405V; P129L; R222C; T44I; Q275H; R380C; A360V; A361V; G115C; L353F;H237Y; L462F; E261G; R4C; S263F; T573I; A318V; G262V; P624L; S430L;T422I; A357S; I100V; E272G; L400F; A192V; D464A; E172D; G262S; L501F;S369F; E172K; G465S; K219R; A411V; A522V; H194Y; S32L; F437L; P181S;P446L; G115V; H532Y; N92H; P13S; A159V; A184S; A306S; I273T; L274F;P13L; R370H; T223I; T590I; E453D; H145Y; K618N; S301F; T153M; V244I;V530I; A127V; L24F; P191L; Q182L; S196L; S248G; S378F; T139I; T434I;A205V; A375V; A411S; C51Y; F300L; M135T; P568S; Q496H; S348P; T412I;T528I; T547I; V447F; or V577I; and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp3 protein: A58T; T1198K; T428I; P153L;S1197R; D218E; S1424F; A1431V; S1285F; P74L; Q1884H; P1326L; L1221F;P141S; P1103S; S126L; Y916H; L557F; E391D; A1311V; S650F; P1103L; Y952H;P340S; A534V; P1787S; L1791F; N1587S; S371N; K1693N; G282V; P278S;T1335I; A1711V; K19R; A994D; K1325R; P822L; K412N; A465V; T1004I; T808I;G489D; S1699F; M1436V; S1265R; V1768G; A231V; M951I; K384N; T1288I;Q966H; R1614K; T1036I; T1306I; A1179V; P395L; N1785D; P679L; S166G;A1769V; T181I; L1718F; P822S; T1022I; A1381V; A602T; I1720V; K837N;T73I; A1033V; S1204; C1223Y; P389L; T398A; M1441I; M494I; T1303I; T181A;P1228L; R1135K; V267F; A1883V; A655V; S1296F; T686I; L198I; P1403S;L781F; T1046A; A1215V; E374D; I205 deletion; V477F; E324K; I707V; P109L;P1558L; P74S; S1212L; S1807F; T819I; T864I; H1000Y; P340L; S697F;T1189I; A480V; D729Y; K1771R; S1717L; T749I; M829I; Q172R; T1482I;A1395V; I385T; M560I; S1206L; S1699P; T1269I; T779I; V1315I; V1795F;V325F; A1892V; A579V; E493G; H1274Y; S1467F; T1063I; T350I; V61F;A1736V; K1804N; R646W; T583I; T611I; V1243I; V190I; A41V; H290Y; H295Y;H342Y; L1244F; Q128H; V1673I; A1305V; A1526S; E948K; L72F; P125S; P402T;A1766V; D1214N; E1271D; G1440D; G283D; K1211N; K902N; K945N; L1839S;L312F; N1263S; P1292S; S1670F; S743A; T771I; V1936I; A1262V; A1321V;A358V; A41T; C55Y; G1273S; K463E; K497Q; P1044S; R30K; S1375F; S1682F;T133I; T1348I; 465I; T1830I; T237I; V1248L; A225V; A496V; G1217R;I1816T; L956I; N1369T; N506S; P153S; P2L; T1275I; T1459I; V1234M; E595D;F90L; G1585S; H1307Y; I1409V; L1034V; L1328F; L292F; N1264; P1326T;S1197G; T1456I; T64I; T703I; T720I; T820I; V1229F; V234I; A1279V; A333V;A54S; D1121G; D1761N; E731D; I1672T; I789V; K1037R; K487N; L142F;N1177H; P1228S; P723S; Q180H; Q474R; Q940L; S370L; T11801; T275I; T422I;T526I; T724I; V1434G; or V207L; or combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp4 protein: F308Y; T295I; M33I; A307V;A457V; G309C; L360F; A231V; H313Y; K399E; V20F; S137L; S34F; A380V;H470Y; T204I; S336L; L264F; L438F; M33L; S209F; C296S; L475I; G79V;T327N; T350I; L206F; M324I; E230G; L436 deletion; T237I; T492I; A260V;A446V; M458I; S395G; S481L; H36Y; T73I; L323F; L349F; S59F; T214I; orT60I; and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp5 protein: G15S; D248E; K90R; L89F; A266V;P108S; A70T; A129V; T45I; G71S; L75F; A191V; L220F; N274D; L67F; P241L;K236R; V157L; K61R; P184S; S62Y; T21I; L50F; P108L; S254F; T93I; A255V;A94V; P132S; A234V; A260V; R60C; P96L; V247F; or T1991; and combinationsthereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp6 protein: L37F; G277S; A46V; L75F; F37deletion; T10I; V149F; L260F; Q208H; M83I; A136V; V145I; N156D; M86I;Y153C; G188V; L230I; F34 deletion; I189V; R233H; V114A; L33F; A287V;H11Y; A287T; A51V; G188S; I162T; M126V; M183I; N40Y; S104; F35L; M58L;or V84F; and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp7 protein: S25L; S26F; L71F; S15T; M75I;or N78S; and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp8 protein: M129I; I156V; T145I; R51C;T123I; L95F; T89I; P133S; S41F; K37N; T141M; V34F; R51L; A14T; A74V;I107V; A16V; P10S; A194V; D30G; A152V; or T1871; and combinationsthereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the nsp9 protein: T77I; T109I; L42F; T34I; T191;M101V; T62I; or T19K; and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the protein product of ORF10: L17P; A28V; P10S;I4L; S23F; R24C; *39Q; Q29 stop; Y14C; R20I; or A8V; and combinationsthereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the protein product of ORF3a: Q57H; G251V; V13L;G196V; A54S; A99V; H93Y; T14I; L46F; Q185H; T175I; Q213K; L108F; K61N;Y264C; A72S; T151I; A23S; G224C; K67N; S171L; W69L; H78Y; K136E; L86F;W131C; L147F; S58N; Y91H; I63T; D155Y; G172C; P240L; Y189C; W131R;KN136NY; T223I; G100C; S195Y; V112F; W131L; G44V; D27H; G174C; K21N;S165F; L65F; T229I; T89I; S74F; A99S; G254R; H204N; K75N; F43L; L53F;Q38P; S26L; S40L; M260I; V256 deletion; K16N; Q218R; S253P; V163L; W69C;A23V; L41F; L106F; V55F; V88A; A99D; E239D; L52F; T24I; A31T; D27Y;I186V; L73F; P104L; D22Y; F114V; L95F; P240S; P42L; T268M; or T32I; andcombinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the protein product of ORF6: I33T; W27L; D53G;F22 deletion; P57L; D61Y; D61L; K42N; D53Y; H3Y; I32T; or R20S; orcombinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the protein product of ORF7a: S81L; A8T; L96F;A50V; V104F; Q62 stop; S83L; E16D; T14I; T28I; V93F; G38V; H47Y; T39I;T120S; Q62 deletion; Q62L; S37T; V104; P34S; P99L; T120I; V108L; H73Y;V24F; V29L; A13T; or L5F; or combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the protein product of ORF7b: C41F; T40I; A43V;L11F; S31L; C41 deletion; H42; H42L; S5L; L20F; L32F; E33 stop; A15S; orF13 deletion; and combinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the protein product of ORF8: E110 stop; G66deletion; S69L; T11I; F104L; F120L; G8R; P38S; D119E; I10S; or I39V; andcombinations thereof.

In some embodiments, the SARS-CoV-2 variant contains one or more of thefollowing mutations in the spike protein: D614G; D936Y; P1263L; L5F;N439K; R21I; D839Y; L54F; A879S; L18F; F1121L; R847K; T478I; A829T;Q675H; S477N; H49Y; T29I; G769V; GI 124V; V1176F; K1073N; P479S; S1252P;Y145 deletion; E583D; R214L; A1020V; Q1208H; D215G; H146Y; S98F; T95I;G1219C; A846V; I197V; R102I; V367F; T572I; A1078S; A831V; P1162L; T73I;A845S; G1219V; H245Y; L8V; Q675R; S254F; V483A; Q677H; D138H; D80Y;M1237T; D1146H; E654D; H655Y; S50L; S939F; S943P; G485R; Q613H; T76I;V341I; M153I; S221L; T859I; W258L; L242F; P681L; V289I; A520S; V1104L;V1228L; L176F; M1237I; T307I; T716I; L141; M1229I; A1087S; P26S; P330S;P384L; R765L; S940F; T323I; V826L; E1202Q; L1203F; L611F; V615I; A262S;A522V; A688V; A706V; A892S; E554D; Q836H; T1027I; T22I; A222V; A27S;A626V; C1247F; K1191N; M731I; P26L; S1147L; S1252F; S255F; V1264L;V308L; D80A; I670L; P251L; P631S; *I274Q; A344S; A771S; A879T; D1084Y;D253G; H1101Y; L1200F; Q14H; Q239K; A623V; D215Y; E1150D; G476S; K77M;M177I; P812S; S704L; T51I; T547I; T791I; V1122L; Y145H; D574Y; G142D;G181V; I834T; N370S; P812L; S12F; T791P; V90F; W152L; A292S; A570V;A647S; A845V; D1163Y; G181R; L84I; L938F; P1143L; P809S; R78M; T1160I;V1133F; V213L; V615F; A831V; D839Y; D839N; D839E; S943P; P1263L; orV622F; and combinations thereof.

Pharmaceutical Compositions and Dosage Forms

A compound of Formula I, Formula II, Formula III, Formula IV, Formula V,Formula VI, Formula VII, Formula VIII, Formula IX, Formula X, or FormulaXIII or a pharmaceutically acceptable salt thereof, can be administeredin an effective amount for the treatment of the 2019 coronavirus disease(COVID-19) caused by the SARS-CoV-2 virus in a host, typically a human,in need thereof. In one embodiment the compound is Compound 1A orCompound 3A or a pharmaceutically acceptable salt thereof, for exampleCompound 2A or Compound 4A. In one embodiment the compound is Compound1B or Compound 3B or a pharmaceutically acceptable salt thereof, forexample Compound 2B or Compound 4B.

The compound or its salt can be provided as the neat chemical but ismore typically administered as a pharmaceutical composition thatincludes an effective amount for a host, typically a human, in need of atreatment for COVID-19. Thus, in one embodiment, the disclosure providespharmaceutical compositions comprising an effective amount of a compoundof Formula I, Formula II, Formula III, Formula IV, Formula V, FormulaVI, Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII ora pharmaceutically acceptable salt thereof, with at least onepharmaceutically acceptable carrier for the treatment of COVID-19. Thepharmaceutical composition may contain a compound of Formula I, FormulaII, Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof, as the only active agent, or, in an alternativeembodiment, in combination with at least one additional active agent.

A compound of Formula I (including but not limited to Compound 1, 1A or1B), Formula II (including but not limited to Compound 3, 3A or 3B),Formula III (including, Formula IIIa, Formula IIIb, Formula IIIc,Formula IIId, Formula IIIe, or Formula IIIf), Formula IV (including,Formula IVa, Formula IVb, Formula IVc, Formula IVd, Formula IVe, orFormula IVf), Formula V, Formula VI, Formula VII, Formula VIII, FormulaIX, Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, can be formulated with one or more pharmaceutically acceptablecarriers. Oral dosage forms are sometimes selected due to ease ofadministration and prospective favorable patient compliance. In oneembodiment, a compound of Formula I, Formula II, Formula III, FormulaIV, Formula V, Formula VI, Formula VII, Formula VIII, Formula IX,Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, is provided in a solid dosage form, such as a tablet or pill,which are well known in the art and described further below. Entericcoated oral tablets may also be used to enhance bioavailability of thecompounds for an oral route of administration. Pharmaceuticalcompositions (formulations) may be administered via oral, parenteral,intravenous, inhalation, intramuscular, topical, transdermal, buccal,subcutaneous, suppository, or other route, including intranasal sprayroutes of delivery.

In one embodiment, a compound of Formula I, Formula II, Formula III,Formula IV, Formula V, Formula VI, Formula VII, Formula VIII, FormulaIX, Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof is administered intravenously. In one non-limiting embodiment, acompound of the present invention is administered intravenously at aloading dose of 550 mg/day and a maintenance dose of 275 mg/day. In oneembodiment, the loading dose is administered once and the maintenancedose is administered twice a day for at least 3, 4, 5, 6, 7, 8, 9, 10,11, or 12 days. In one non-limiting embodiment, an intravenous loadingdose is 550 mg/day of Compound 1 (i.e., 600 mg/day hemisulfate salt ofCompound 1), and a maintenance dose is 275 mg/day (i.e, 300 mg/day ofhemisulfate salt)).

Effective dosage form will depend upon thebioavailability/pharmacokinetic of the particular agent chosen as wellas the severity of disease in the patient. A compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, can be administered, forexample, in one or more tablets, capsules, injections, intravenousformulations, suspensions, liquids, emulsions, implants, particles,spheres, creams, ointments, suppositories, inhalable forms, transdermalforms, buccal, sublingual, topical, gel, mucosal, and the like.

Intravenous and intramuscular formulations are often administered insterile saline. One of ordinary skill in the art may modify theformulations to render them more soluble in water or another vehicle,for example, this can be easily accomplished by minor modifications(salt formulation, esterification, etc.).

The pharmaceutical compositions contemplated here optionally include acarrier, as described further below. Carriers must be of sufficientlyhigh purity and sufficiently low toxicity to render them suitable foradministration to the patient being treated. The carrier can be inert orit can possess pharmaceutical benefits of its own. The amount of carrieremployed in conjunction with the compound is sufficient to provide apractical quantity of material for administration per unit dose of thecompound. Representative carriers include solvents, diluents, pHmodifying agents, preservatives, antioxidants, suspending agents,wetting agent, viscosity agents, tonicity agents, stabilizing agents,and combinations thereof. In some embodiments, the carrier is an aqueouscarrier.

One or more viscosity agents may be added to the pharmaceuticalcomposition to increase the viscosity of the composition as desired.Examples of useful viscosity agents include, but are not limited to,hyaluronic acid, sodium hyaluronate, carbomers, polyacrylic acid,cellulosic derivatives, polycarbophil, polyvinylpyrrolidone, gelatin,dextin, polysaccharides, polyacrylamide, polyvinyl alcohol (includingpartially hydrolyzed polyvinyl acetate), polyvinyl acetate, derivativesthereof and mixtures thereof.

Solutions, suspensions, or emulsions for administration may be bufferedwith an effective amount of buffer necessary to maintain a pH suitablefor the selected administration. Suitable buffers are well known bythose skilled in the art. Some examples of useful buffers are acetate,borate, carbonate, citrate, and phosphate buffers.

To prepare the pharmaceutical compositions according to the presentinvention, a therapeutically effective amount of a compound of FormulaI, Formula II, Formula III, Formula IV, Formula V, Formula VI, FormulaVII, Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof may be admixed with apharmaceutically acceptable carrier according to conventionalpharmaceutical compounding techniques to produce a dose. A carrier maytake a wide variety of forms depending on the form of preparationdesired for administration, e.g., oral or parenteral.

In preparing pharmaceutical compositions in oral dosage form, any of theusual pharmaceutical media may be used. Thus, for liquid oralpreparations such as suspensions, elixirs, and solutions, suitablecarriers and additives including water, glycols, oils, alcohols,flavoring agents, preservatives, coloring agents, and the like may beused. For solid oral preparations such as powders, tablets, capsules,and for solid preparations such as suppositories, suitable carriers andadditives including starches, sugar carriers, such as dextrose,mannitol, lactose, and related carriers, diluents, granulating agents,lubricants, binders, disintegrating agents, and the like may be used. Ifdesired, the tablets or capsules may be enteric-coated or sustainedrelease by standard techniques. The use of these dosage forms maysignificantly enhance the bioavailability of the compounds in thepatient.

For parenteral formulations, the carrier will usually comprise sterilewater or aqueous sodium chloride solution, though other ingredients,including those which aid dispersion, also may be included. Of course,where sterile water is to be used and maintained as sterile, thecompositions and carriers must also be sterilized. Injectablesuspensions may also be prepared, in which case appropriate liquidcarriers, suspending agents, and the like may be employed.

Liposomal suspensions (including liposomes targeted to viral antigens)may also be prepared by conventional methods to produce pharmaceuticallyacceptable carriers. This may be appropriate for the delivery of freenucleosides, acyl/alkyl nucleosides or phosphate ester pro-drug forms ofthe nucleoside compounds according to the present invention.

Amounts and weights mentioned in this disclosure typically refer to thefree form (i.e., non-salt, hydrate or solvate form). The typicallyvalues described herein represent free-form equivalents, i.e.,quantities as if the free form would be administered. If salts areadministered the amounts need to be calculated in function of themolecular weight ratio between the salt and the free form.

The amount of a compound of Formula I, Formula II, Formula III, FormulaIV, Formula V, Formula VI, Formula VII, Formula VIII, Formula IX,Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, in the pharmaceutically acceptable formulation according to thepresent invention is an effective amount to achieve the desired outcomeof treating COVID-19, reducing the likelihood of COVID-19, or theinhibition, reduction, and/or elimination of COVID-19 or its secondaryeffects, including disease states, conditions, and/or complicationswhich occur secondary to the virus. As non-limiting embodiments, atherapeutically effective amount of the present compounds in apharmaceutical dosage form may range, for example, from about 0.001mg/kg to about 100 mg/kg per day or more. A compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, may for example innon-limiting embodiments be administered in amounts ranging from about0.1 mg/kg to about 15 mg/kg per day of the patient, depending upon thepharmacokinetics of the agent in the patient.

The weight of active compound in the dosage form described herein iswith respect to either the free form or the salt form of the compoundunless otherwise specifically indicated. For example, approximately 600mg of Compound 2 is the equivalent of approximately 550 mg of Compound1.

In certain embodiments, the pharmaceutical composition is in a dosageform that contains from about 1 mg to about 2000 mg, from about 10 mg toabout 1000 mg, from about 100 mg to about 800 mg, from about 200 mg toabout 600 mg, from about 300 mg to about 500 mg, or from about 400 mg toabout 450 mg of a compound of Formula I, Formula II, Formula III,Formula IV, Formula V, Formula VI, Formula VII, Formula VIII, FormulaIX, Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, in a unit dosage form.

In certain embodiments, the pharmaceutical composition is in a dosageform, for example in a solid dosage form, that contains up to about 10,about 50, about 100, about 125, about 150, about 175, about 200, about225, about 250, about 275, about 300, about 325, about 350, about 375,about 400, about 425, about 450, about 475, about 500, about 525, about550, about 575, about 600, about 625, about 650, about 675, about 700,about 725, about 750, about 775, about 800, about 825, about 850, about875, about 900, about 925, about 950, about 975, about 1000 mg, about1050 mg, about 1100 mg, about 1150 mg, about 1200 mg, about 1250 mg,about 1300 mg, about 1350 mg, about 1400 mg, about 1450 mg, about 1500mg, about 1550 mg, about 1600 mg, about 1650 mg, about 1700 mg or moreof a compound of Formula I, Formula II, Formula III, Formula IV, FormulaV, Formula VI, Formula VII, Formula VIII, Formula IX, Formula X, orFormula XIII or a pharmaceutically acceptable salt thereof, in a unitdosage form.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof, for example Compound 1 or Compound 2, is administered atan initial dose (or loading dose) followed by a maintenance dose of atleast about 300 mg, at least about 350 mg, at least about 400 mg, atleast about 450 mg, at least about 500 mg, at least about 550 mg, atleast about 650, or at least about 750 and the dose is taken once ortwice a day. In one embodiment, the loading dose is about 1.5 timesgreater, about 2 times greater, about 2.5 times greater, or 3-fold timesgreater than the maintenance dose. In one embodiment, the loading doseis administered once, twice, three, four, or more times before the firstmaintenance dose.

In one embodiment, the pharmaceutical composition is in a dosage form,for example in a solid dosage form, that contains at least 500 mg, atleast 550 mg, 600 mg, at least 700 mg, at least 800 mg, at least 900 mg,at least 1000 mg, at least 1100 mg, at least 1200, at least 1300 mg, atleast 1400 mg, or at least 1500 mg of a compound of Formula I, FormulaII, Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof, in a unit dosage form.

In certain embodiments, the pharmaceutical composition, for example, asolid dosage form, contains at least about 450 mg, 550 mg, 650 mg, 750mg or 850 mg of Compound 1 or Compound 3. In one embodiment, thepharmaceutical composition contains at least about 500 mg, at leastabout 550 mg, or at least about 600 mg of Compound 1 or Compound 3 andthe composition is administered twice a day. In one embodiment, thepharmaceutical composition contains at least about 550 mg of Compound 1and the pharmaceutical composition is administered twice a day. In oneembodiment, the pharmaceutical composition is administered at an initialdose (or loading dose) of at least about 900 mg, 1000 mg, 1100 mg, 1100mg, or 1200 mg of Compound 1 followed by a dose of at least about 400mg, at least about 450 mg, at least about 500 mg, at least about 550, atleast about 600 mg, or at least about 650 mg of Compound 1 twice a day.In one embodiment, the pharmaceutical composition is administered at aninitial dose (or loading dose) of at least about 1100 mg of Compound 1followed by a dose of at least about 450 mg, 550 mg, 650 mg, 750 mg, or850 mg of Compound 1 twice a day. In one embodiment, the pharmaceuticalcomposition is administered at an initial dose (or loading dose) of atleast about 1100 mg of Compound 1 followed by a dose of at least about550 mg of Compound 1 twice a day. In one embodiment, the maintenancedose is administered for at about 4, 5, 6, 7, 8, 9, 10, or more days. Inone embodiment, Compound 1 is Compound 1A. In one embodiment, Compound 1is Compound 1B.

In one embodiment, an effective amount of a compound of Formula I:

or a pharmaceutically acceptable salt thereof, optionally in apharmaceutically acceptable carrier, is administered for the treatmentof the 2019 coronavirus disease (COVID-19) caused by the SARS-CoV-2virus in a human in need thereof wherein the compound is administeredaccording to the following schedule:

-   -   (i) a single loading dose of 1100 mg of free base in one day;        followed by    -   (ii) a maintenance dose of 550 mg of free base per day.

In one embodiment, an effective amount of a compound of the Formula:

or a pharmaceutically acceptable salt thereof, optionally in apharmaceutically acceptable carrier, is administered for the treatmentof the 2019 coronavirus disease (COVID-19) caused by the SARS-CoV-2virus in a human in need thereof wherein the compound is administeredaccording to the following schedule:

-   -   (i) a single loading dose of 1100 mg of free base in one day;        followed by    -   (ii) a maintenance dose of 550 mg of free base per day.

In one embodiment, an effective amount of a compound of the Formula:

optionally in a pharmaceutically acceptable carrier, is administered forthe treatment of the 2019 coronavirus disease (COVID-19) caused by theSARS-CoV-2 virus in a human in need thereof wherein the compound isadministered according to the following schedule:

-   -   (i) a single loading dose of 1200 mg of salt in one day;        followed by    -   (ii) a maintenance dose of 600 mg of salt per day.

In certain embodiments, the pharmaceutical composition, for example, asolid dosage form, contains at least about 400 mg, at least about 500mg, 600 mg, 700 mg, or 800 mg of Compound 2 or Compound 4. In oneembodiment, the pharmaceutical composition contains at least about 500mg, at least about 600 mg, or at least about 700 mg of Compound 2 orCompound 4 and the composition is administered twice a day. In oneembodiment, the pharmaceutical composition contains at least about 600mg of Compound 2 and the pharmaceutical composition is administeredtwice a day. In one embodiment, the pharmaceutical composition isadministered at an initial dose (or loading dose) of at least about 900mg, 1000 mg, 1100 mg, 1200 mg, or 1300 mg of Compound 2 followed by adose of at least about 400 mg, 500 mg, 600 mg, 700 mg, or 800 mg ofCompound 2 once, twice, or three times a day. In one embodiment, thepharmaceutical composition is administered at an initial dose (orloading dose) of at least about 1000 mg, 1200 mg, or 1400 mg of Compound2 followed by a dose of at least about 600 mg of Compound 2 twice a day.In one embodiment, the pharmaceutical composition is administered at aninitial dose (or loading dose) of at least about 1200 mg of Compound 2followed by a dose of at least about 400 mg, 500 mg, 600 mg, 700 mg, or800 mg of Compound 2 twice a day. In one embodiment, the pharmaceuticalcomposition is administered at an initial dose (or loading dose) of atleast about 1200 mg of Compound 2 followed by a dose of at least about600 mg of Compound 2 twice a day. In one embodiment, the maintenancedose is administered for at about 4, 5, 6, 7, 8, 9, 10, or more days. Inone embodiment, Compound 2 is Compound 2A. In one embodiment, Compound 2is Compound 1B.

In certain embodiments, a compound of Formula I, Formula II, FormulaIII, Formula IV, Formula V, Formula VI, Formula VII, Formula VIII,Formula IX, Formula X, or Formula XIII or a pharmaceutically acceptablesalt thereof, is administered for at least five days, six days, sevendays, eight days, nine days, ten days, two weeks, three weeks, onemonth, at least two months, at least three months, at least four months,at least five months, at least six months or more. In one embodiment, acompound of Formula I, Formula II, Formula III, Formula IV, Formula V,Formula VI, Formula VII, Formula VIII, Formula IX, Formula X, or FormulaXIII or a pharmaceutically acceptable salt thereof, is administeredonce, twice, three, or more times a day. In one embodiment, it isadministered orally twice a day.

For purposes of the present invention, a prophylactically or preventiveeffective amount of the compositions according to the present inventionmay generally fall within the ranges set out above, and can bedetermined in the best judgement of the health care provider. In oneembodiment, a compound of the present invention is administeredseasonally as the risk of the virus increases to prevent infection, orcan be administered, for example, before, during and/or after travel orexposure.

One of ordinary skill in the art will recognize that a therapeuticallyeffective amount will vary with the infection or condition to betreated, its severity, the treatment regimen to be employed, thepharmacokinetic of the agent used, as well as the patient or subject(animal or human) to be treated, and such therapeutic amount can bedetermined by the attending physician or specialist.

Solid Dosage Forms

An aspect of the invention is a solid dosage form that includes aneffective amount of a compound of Formula I (including but not limitedto Compound 1, 1A, 1B, 2, 2A or 2B), Formula II (including but notlimited to Compound 3), Formula III (including Formula IIIa, FormulaIIIb, Formula IIIc, Formula IIId, Formula IIIe, or Formula IIIf),Formula IV (including Formula IVa, Formula IVb, Formula IVc, FormulaIVd, Formula IVe, or Formula IVf), Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, optionally in apharmaceutically acceptable carrier.

In one embodiment, the solid dosage form includes a spray dried soliddispersion of a compound of Formula I, Formula II, Formula III, FormulaIV, Formula V, Formula VI, Formula VII, Formula VIII, Formula IX,Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, and the composition is suitable for oral delivery. In anotherembodiment, the solid dosage form is a granulo layered solid dispersionof a compound of Formula I, Formula II, Formula III, Formula IV, FormulaV, Formula VI, Formula VII, Formula VIII, Formula IX, Formula X, orFormula XIII or a pharmaceutically acceptable salt thereof, and thecomposition is suitable for oral delivery.

In other embodiments, the solid dispersion also contains at least oneexcipient selected from copovidone, poloxamer and HPMC-AS. In oneembodiment the poloxamer is Poloxamer 407 or a mixture of poloxamersthat may include Poloxamer 407. In one embodiment HPMC-AS is HPMC-AS-L.

In other embodiments, a solid dosage form prepared from a compound ofFormula I, Formula II, Formula III, Formula IV, Formula V, Formula VI,Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, also comprises one or more ofthe following excipients: a phosphoglyceride; phosphatidylcholine;dipalmitoyl phosphatidylcholine (DPPC); dioleylphosphatidyl ethanolamine(DOPE); dioleyloxypropyltriethylammonium (DOTMA);dioleoylphosphatidylcholine; cholesterol; cholesterol ester;diacylglycerol; diacylglycerolsuccinate; diphosphatidyl glycerol (DPPG);hexanedecanol; fatty alcohol such as polyethylene glycol (PEG);polyoxyethylene-9-lauryl ether; a surface active fatty acid, such aspalmitic acid or oleic acid; fatty acid; fatty acid monoglyceride; fattyacid diglyceride; fatty acid amide; sorbitan trioleate (Span® 85)glycocholate; sorbitan monolaurate (Span® 20); polysorbate 20 (Tween®20); polysorbate 60 (Tween® 60); polysorbate 65 (Tween®65); polysorbate80 (Tween® 80); polysorbate 85 (Tween®85); polyoxyethylene monostearate;surfactin; a poloxomer; a sorbitan fatty acid ester such as sorbitantrioleate; lecithin; lysolecithin; phosphatidylserine;phosphatidylinositol; sphingomyelin; phosphatidylethanolamine(cephalin); cardiolipin; phosphatidic acid; cerebroside;dicetylphosphate; dipalmitoylphosphatidylglycerol; stearylamine;dodecylamine; hexadecyl-amine; acetyl palmitate; glycerol ricinoleate;hexadecyl stearate; isopropyl myristate; tyloxapol; poly(ethyleneglycol)5000-phosphatidylethanolamine; poly(ethyleneglycol)400-monostearate; phospholipid; synthetic and/or naturaldetergent having high surfactant properties; deoxycholate; cyclodextrin;chaotropic salt; ion pairing agent; glucose, fructose, galactose,ribose, lactose, sucrose, maltose, trehalose, cellbiose, mannose,xylose, arabinose, glucoronic acid, galactoronic acid, mannuronic acid,glucosamine, galatosamine, and neuramic acid; pullulan, cellulose,microcrystalline cellulose, silicified microcrystalline cellulose,hydroxypropyl methylcellulose (HPMC), hydroxycellulose (HC),methylcellulose (MC), dextran, cyclodextran, glycogen,hydroxyethylstarch, carageenan, glycon, amylose, chitosan,N,O-carboxylmethylchitosan, algin and alginic acid, starch, chitin,inulin, konjac, glucommannan, pustulan, heparin, hyaluronic acid,curdlan, and xanthan, mannitol, sorbitol, xylitol, erythritol, maltitol,and lactitol, a pluronic polymer, polyethylene, polycarbonate (e.g.,poly(1,3-dioxan-2one)), polyanhydride (e.g., poly(sebacic anhydride)),polypropylfumerate, polyamide (e.g. polycaprolactam), polyacetal,polyether, polyester (e.g., polylactide, polyglycolide,polylactide-co-glycolide, polycaprolactone, polyhydroxyacid (e.g.,poly((β-hydroxyalkanoate))), poly(orthoester), polycyanoacrylate,polyvinyl alcohol, polyurethane, polyphosphazene, polyacrylate,polymethacrylate, polyurea, polystyrene, and polyamine, polylysine,polylysine-PEG copolymer, and poly(ethyleneimine), poly(ethyleneimine)-PEG copolymer, glycerol monocaprylocaprate, propylene glycol,Vitamin E TPGS (also known as d-α-Tocopheryl polyethylene glycol 1000succinate), gelatin, titanium dioxide, polyvinylpyrrolidone (PVP),hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose (HPC),methyl cellulose (MC), block copolymers of ethylene oxide and propyleneoxide (PEO/PPO), polyethyleneglycol (PEG), sodium carboxymethylcellulose(NaCMC), or hydroxypropylmethyl cellulose acetate succinate (HPMCAS).

In other embodiments, a solid dosage form prepared from a compound ofFormula I, Formula II, Formula III, Formula IV, Formula V, Formula VI,Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, also comprises one or more ofthe following surfactants: polyoxyethylene glycol, polyoxypropyleneglycol, decyl glucoside, lauryl glucoside, octyl glucoside,polyoxyethylene glycol octylphenol, Triton X-100, glycerol alkyl ester,glyceryl laurate, cocamide MEA, cocamide DEA, dodecyldimethylamineoxide, and poloxamers. Examples of poloxamers include, poloxamers 188,237, 338 and 407. These poloxamers are available under the trade namePluronic® (available from BASF, Mount Olive, N.J.) and correspond toPluronic® F-68, F-87, F-108 and F-127, respectively. Poloxamer 188(corresponding to Pluronic® F-68) is a block copolymer with an averagemolecular mass of about 7,000 to about 10,000 Da, or about 8,000 toabout 9,000 Da, or about 8,400 Da. Poloxamer 237 (corresponding toPluronic® F-87) is a block copolymer with an average molecular mass ofabout 6,000 to about 9,000 Da, or about 6,500 to about 8,000 Da, orabout 7,700 Da. Poloxamer 338 (corresponding to Pluronic® F-108) is ablock copolymer with an average molecular mass of about 12,000 to about18,000 Da, or about 13,000 to about 15,000 Da, or about 14,600 Da.Poloxamer 407 (corresponding to Pluronic® F-127) is apolyoxyethylene-polyoxypropylene triblock copolymer in a ratio ofbetween about E101 P56 E101 to about E106 P70 E106, or about E101P56E101, or about E106 P70 E106, with an average molecular mass of about10,000 to about 15,000 Da, or about 12,000 to about 14,000 Da, or about12,000 to about 13,000 Da, or about 12,600 Da.

In yet other embodiments, a solid dosage form prepared from a compoundof Formula I, Formula II, Formula III, Formula IV, Formula V, FormulaVI, Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII ora pharmaceutically acceptable salt thereof, also comprises one or moreof the following surfactants: polyvinyl acetate, cholic acid sodiumsalt, dioctyl sulfosuccinate sodium, hexadecyltrimethyl ammoniumbromide, saponin, sugar esters, Triton X series, sorbitan trioleate,sorbitan mono-oleate, polyoxyethylene (20) sorbitan monolaurate,polyoxyethylene (20) sorbitan monooleate, oleyl polyoxyethylene (2)ether, stearyl polyoxyethylene (2) ether, lauryl polyoxyethylene (4)ether, block copolymers of oxyethylene and oxypropylene, diethyleneglycol dioleate, tetrahydrofurfuryl oleate, ethyl oleate, isopropylmyristate, glyceryl monooleate, glyceryl monostearate, glycerylmonoricinoleate, cetyl alcohol, stearyl alcohol, cetylpyridiniumchloride, benzalkonium chloride, olive oil, glyceryl monolaurate, cornoil, cotton seed oil, and sunflower seed oil.

In alternative embodiments, a solid dosage form prepared from a compoundof Formula I, Formula II, Formula III, Formula IV, Formula V, FormulaVI, Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII ora pharmaceutically acceptable salt thereof, is prepared by a processthat includes solvent or dry granulation optionally followed bycompression or compaction, spray drying, nano-suspension processing, hotmelt extrusion, extrusion/spheronization, molding, spheronization,layering (e.g., spray layering suspension or solution), or the like.Examples of such techniques include direct compression, usingappropriate punches and dies, for example wherein the punches and diesare fitted to a suitable tableting press; wet granulation using suitablegranulating equipment such as a high shear granulator to form wettedparticles to be dried into granules; granulation followed by compressionusing appropriate punches and dies, wherein the punches and dies arefitted to a suitable tableting press; extrusion of a wet mass to form acylindrical extrudate to be cut into desire lengths or break intolengths under gravity and attrition; extrusion/spheronization where theextrudate is rounded into spherical particles and densified byspheronization; spray layering of a suspension or solution onto an inertcore using a technique such as a convention pan or Wurster column;injection or compression molding using suitable molds fitted to acompression unit; and the like.

Exemplary disintegrants include alginic acid, carboxymethylcellulosecalcium, carboxymethylcellulose sodium, cross-linked sodiumcarboxymethylcellulose (sodium croscarmellose), powdered cellulose,chitosan, croscarmellose sodium, crospovidone, guar gum, low substitutedhydroxypropyl cellulose, methyl cellulose, microcrystalline cellulose,sodium alginate, sodium starch glycolate, partially pregelatinizedstarch, pregelatinized starch, starch, sodium carboxymethyl starch, andthe like, or a combination thereof.

Exemplary lubricants include calcium stearate, magnesium stearate,glyceryl behenate, glyceryl palmitostearate, hydrogenated castor oil,light mineral oil, sodium lauryl sulfate, magnesium lauryl sulfate,sodium stearyl fumarate, stearic acid, zinc stearate, silicon dioxide,colloidal silicon dioxide, dimethyldichlorosilane treated with silica,talc, or a combination thereof.

The dosage form cores described herein may be coated to result in coatedtablets. The dosage from cores can be coated with a functional ornon-functional coating, or a combination of functional andnon-functional coatings. “Functional coating” includes tablet coatingsthat modify the release properties of the total composition, forexample, a sustained-release or delayed-release coating. “Non-functionalcoating” includes a coating that is not a functional coating, forexample, a cosmetic coating. A non-functional coating can have someimpact on the release of the active agent due to the initialdissolution, hydration, perforation of the coating, etc., but would notbe considered to be a significant deviation from the non-coatedcomposition. A non-functional coating can also mask the taste of theuncoated composition including the active pharmaceutical ingredient. Acoating may comprise a light blocking material, a light absorbingmaterial, or a light blocking material and a light absorbing material.

Exemplary polymethacrylates include copolymers of acrylic andmethacrylic acid esters, such as a. an aminomethacrylate copolymerUSP/NF such as a poly(butyl methacrylate, (2-dimethylaminoethyl)methacrylate, methyl methacrylate) 1:2:1 (e.g., EUDRAGIT E100, EUDRAGIT EPO, and EUDRAGIT E 12.5; CAS No. 24938-16-7); b. apoly(methacrylic acid, ethyl acrylate) 1:1 (e.g., EUDRAGIT L30 D-55,EUDRAGIT L100-55, EASTACRYL 30D, KOLLICOAT MAE 30D AND 30DP; CAS No.25212-88-8); c. a poly(methacrylic acid, methyl methacrylate) 1:1 (e.g.,EUDRAGIT L 100, EUDRAGIT L 12.5 and 12.5 P; also known as methacrylicacid copolymer, type A NF; CAS No. 25806-15-1); d. a poly(methacrylicacid, methyl methacrylate) 1:2 (e.g., EUDRAGIT S 100, EUDRAGIT S 12.5and 12.5P; CAS No. 25086-15-1); e. a poly(methyl acrylate, methylmethacrylate, methacrylic acid) 7:3:1 (e.g., Eudragit FS 30 D; CAS No.26936-24-3); f. a poly(ethyl acrylate, methylmethacrylate,trimethylammonioethyl methacrylate chloride) 1:2:0.2 or 1:2:0.1 (e.g.,EUDRAGITS RL 100, RL PO, RL 30 D, RL 12.5, RS 100, RS PO, RS 30 D, or RS12.5; CAS No. 33434-24-1); g. a poly(ethyl acrylate, methylmethacrylate) 2:1 (e.g., EUDRAGIT NE 30 D, Eudragit NE 40D, Eudragit NM30D; CAS No. 9010-88-2); and the like, or a combination thereof.

Suitable alkylcelluloses include, for example, methylcellulose,ethylcellulose, and the like, or a combination thereof. Exemplary waterbased ethylcellulose coatings include AQUACOAT, a 30% dispersion furthercontaining sodium lauryl sulfate and cetyl alcohol, available from FMC,Philadelphia, PA; SURELEASE a 25% dispersion further containing astabilizer or other coating component (e.g., ammonium oleate, dibutylsebacate, colloidal anhydrous silica, medium chain triglycerides, etc.)available from Colorcon, West Point, PA; ethyl cellulose available fromAqualon or Dow Chemical Co (Ethocel), Midland, MI Those skilled in theart will appreciate that other cellulosic polymers, including otheralkyl cellulosic polymers, can be substituted for part or all of theethylcellulose.

Other suitable materials that can be used to prepare a functionalcoating include hydroxypropyl methylcellulose acetate succinate(HPMCAS); cellulose acetate phthalate (CAP); a polyvinylacetatephthalate; neutral or synthetic waxes, fatty alcohols (such as lauryl,myristyl, stearyl, cetyl or specifically cetostearyl alcohol), fattyacids, including fatty acid esters, fatty acid glycerides (mono-, di-,and tri-glycerides), hydrogenated fats, hydrocarbons, normal waxes,stearic acid, stearyl alcohol, hydrophobic and hydrophilic materialshaving hydrocarbon backbones, or a combination thereof. Suitable waxesinclude beeswax, glycowax, castor wax, carnauba wax, microcrystallinewax, candelilla, and wax-like substances, e.g., material normally solidat room temperature and having a melting point of from about 30° C. toabout 100° C., or a combination thereof.

In other embodiments, a functional coating may include digestible, longchain (e.g., C8-C50, specifically C12-C40), substituted or unsubstitutedhydrocarbons, such as fatty acids, fatty alcohols, glyceryl esters offatty acids, mineral and vegetable oils, waxes, or a combinationthereof. Hydrocarbons having a melting point of between about 25° C. andabout 90° C. may be used. Specifically, long chain hydrocarbonmaterials, fatty (aliphatic) alcohols can be used.

The coatings can optionally contain additional pharmaceuticallyacceptable excipients such as a plasticizer, a stabilizer, awater-soluble component (e.g., pore formers), an anti-tacking agent(e.g., talc), a surfactant, and the like, or a combination thereof.

A functional coating may include a release-modifying agent, whichaffects the release properties of the functional coating. Therelease-modifying agent can, for example, function as a pore-former or amatrix disrupter. The release-modifying agent can be organic orinorganic, and include materials that can be dissolved, extracted orleached from the coating in the environment of use. Therelease-modifying agent can comprise one or more hydrophilic polymersincluding cellulose ethers and other cellulosics, such as hydroxypropylmethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, methylcellulose, cellulose acetate phthalate, or hydroxypropyl methylcelluloseacetate phthalate; povidone; polyvinyl alcohol; an acrylic polymer, suchas gastric soluble Eudragit FS 30D, pH sensitive Eudragit L30D 55, L100, S 100, or L 100-55; or a combination thereof. Other exemplaryrelease-modifying agents include a povidone; a saccharide (e.g.,lactose, and the like); a metal stearate; an inorganic salt (e.g.,dibasic calcium phosphate, sodium chloride, and the like); apolyethylene glycol (e.g., polyethylene glycol (PEG) 1450, and thelike); a sugar alcohol (e.g., sorbitol, mannitol, and the like); analkali alkyl sulfate (e.g., sodium lauryl sulfate); a polyoxyethylenesorbitan fatty acid ester (e.g., polysorbate); or a combination thereof.Exemplary matrix disrupters include water insoluble organic or inorganicmaterial. Organic polymers including but not limited to cellulose,cellulose ethers such as ethylcellulose, cellulose esters such ascellulose acetate, cellulose acetate butyrate and cellulose acetatepropionate; and starch can function as matrix disrupters. Examples orinorganic disrupters include many calcium salts such as mono-, di- andtri calcium phosphate; silica and, talc.

The coating may optionally contain a plasticizer to improve the physicalproperties of the coating. For example, because ethylcellulose has arelatively high glass transition temperature and does not form flexiblefilms under normal coating conditions, it may be advantageous to addplasticizer to the ethylcellulose before using the same as a coatingmaterial. Generally, the amount of plasticizer included in a coatingsolution is based on the concentration of the polymer, e.g., can be fromabout 1% to about 200% depending on the polymer but is most often fromabout 1 wt % to about 100 wt % of the polymer. Concentrations of theplasticizer, however, can be determined by routine experimentation.

Examples of plasticizers for ethylcellulose and other celluloses includeplasticizers such as dibutyl sebacate, diethyl phthalate, triethylcitrate, tributyl citrate, triacetin, or a combination thereof, althoughit is possible that other water-insoluble plasticizers (such asacetylated monoglycerides, phthalate esters, castor oil, etc.) can beused.

Examples of plasticizers for acrylic polymers include citric acid esterssuch as triethyl citrate NF, tributyl citrate, dibutyl phthalate,1,2-propylene glycol, polyethylene glycols, propylene glycol, diethylphthalate, castor oil, triacetin, or a combination thereof, although itis possible that other plasticizers (such as acetylated monoglycerides,phthalate esters, castor oil, etc.) can be used.

Suitable methods can be used to apply the coating material to thesurface of the dosage form cores. Processes such as simple or complexcoacervation, interfacial polymerization, liquid drying, thermal andionic gelation, spray drying, spray chilling, fluidized bed coating, pancoating, or electrostatic deposition may be used.

In certain embodiments, an optional intermediate coating is used betweenthe dosage form core and an exterior coating. Such an intermediatecoating can be used to protect the active agent or other component ofthe core subunit from the material used in the exterior coating or toprovide other properties. Exemplary intermediate coatings typicallyinclude water-soluble film forming polymers. Such intermediate coatingsmay include film forming polymers such as hydroxyethyl cellulose,hydroxypropyl cellulose, gelatin, hydroxypropyl methylcellulose,polyethylene glycol, polyethylene oxide, and the like, or a combinationthereof; and a plasticizer. Plasticizers can be used to reducebrittleness and increase tensile strength and elasticity. Exemplaryplasticizers include polyethylene glycol propylene glycol and glycerin.

Combination and Alternation Therapy

The compounds or their pharmaceutically acceptable salts as describedherein can be administered on top of the current standard of care forCOVID patients, or in combination or alternation with any other compoundor therapy that the healthcare provider deems beneficial for thepatient. The combination and/or alternation therapy can be therapeutic,adjunctive, or palliative.

It has been observed that COVID patients can pass through various stagesof disease, and that the standard of care can differ based on what stageof illness the patient presents with or advances to. COVID is noteworthyfor the development of “cross-talk” between the immune system and thecoagulation system. As the disease progresses, the patient can mount anoverreaction by the immune system, which can lead to a number of seriousimplications, including a cytokine storm. Via the cross-talk between theimmune system and the coagulation system, the patient can begin clottingin various areas of the body, including the respiratory system, brain,heart and other organs. Multiple clots throughout the body have beenobserved in COVID patients, requiring anticoagulant therapy. It isconsidered that these clots may cause long term, or even permanentdamage if not treated and disease alleviated.

More specifically, COVID-19 has been described as progressing throughthree general stages of illness: stage 1 (early infection), stage 2(pulmonary phase), and stage 3 (hyperinflammation phase/cytokine storm).

Stage 1 is characterized by non-specific, and often mild, symptoms.Viral replication is occurring, and it is appropriate to begin immediatetreatment with the compounds described herein and perhaps in combinationor alternation with another anti-viral therapy. Interferon-β may also beadministered to augment the innate immune response to the virus. In oneembodiment, therefore, a compound of Formula I, Formula II, Formula III,Formula IV, Formula V, Formula VI, Formula VII, Formula VIII, FormulaIX, Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof is used in an effective amount in combination or alternationwith interferon-3 and or an additional anti-viral drug. Zinc supplementsand or Vitamin C is also sometimes administered at this stage or as theillness progresses.

Stage 2 of COVID-19 is the pulmonary phase where patients may experienceacute hypoxemic respiratory failure. In fact, the primary organ failureof COVID-19 is hypoxemic respiratory failure. It has been shown thatmoderate immunosuppression via a steroid, for example, dexamethasone,can be beneficial to patients with acute hypoxemic respiratory failureand/or patients on mechanical ventilation. In one embodiment, a compoundof Formula I, Formula II, Formula III, Formula IV, Formula V, FormulaVI, Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII ora pharmaceutically acceptable salt thereof is used in an effectiveamount in combination with a corticosteroid which may be aglucocorticoid. Non-limiting examples are budesonide (Entocort EC),bethamethasone, (Celestone), prednisone (Prednisone Intensol),prednisolone (Orapred, Prelone), triamcinolone (AristospanIntra-Articular, Aristospan Intralesional, Kenalog), methylprednisolone(Medrol, Depo-Medrol, Solu-Medrol), hydrocortisone, or dexamethasone(Dexamethasone Intensol, DexPak 10 Day, DexPak 13 Day, DexPak 6 Day).

The NS5B inhibitor Remdesivir has provided mixed results when given toCOVID-19 patients. It can only be administered in a hospital setting,and only by intravenous injection, typically three times a day, whichmakes it inappropriate for mild to moderate COVID-19 patients. In oneembodiment, a compound of Formula I, Formula II, Formula III, FormulaIV, Formula V, Formula VI, Formula VII, Formula VIII, Formula IX,Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, is administered in combination or in alternation withRemdesivir to amplify the overall antiviral effect.

Stage 3, the final stage of the disease, is characterized by progressivedisseminated intravascular coagulation (DIC), a condition in which smallblood clots develop throughout the bloodstream. This stage also caninclude multi-organ failure (e.g. vasodilatory shock, myocarditis). Ithas also been observed that many patients respond to this severe stageof COVID-19 infection with a “cytokine storm.” There does appear to be abi-directional, synergistic relationship between DIC and cytokine storm.To combat DIC, patients are often administered an anti-coagulant agent,which may, for example, be an indirect thrombin inhibitor or a directoral anticoagulant (“DOAC”). Non-limiting examples are low-molecularweight heparin, warfarin, bivalirudin (Angiomax), rivaroxaban (Xarelto),dabigatran (Pradaxa), apixaban (Eliquis), or edoxaban (Lixiana). In oneembodiment, a compound of Formula I, Formula II, Formula III, FormulaIV, Formula V, Formula VI, Formula VII, Formula VIII, Formula IX,Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, is administered in combination or in alternation withanti-coagulant therapy. In some severe cases of clotting in COVIDpatients, TPA can be administered (tissue plasminogen activator).

It has been observed that high levels of the cytokine interleukin-6(IL-6) are a precursor to respiratory failure and death in COVID-19patients. To treat this surge of an immune response, which mayconstitute a cytokine storm, patients can be administered anIL-6-targeting monoclonal antibody, pharmaceutical inhibitor or proteindegrader such as a bispecific compound that binds to IL-6 and also to aprotein that mediates degradation. Examples of antibodies includetocilizumab, sarilumab, siltuximab, olokizumab and clazakizumab. In oneembodiment, a compound of Formula I, Formula II, Formula III, FormulaIV, Formula V, Formula VI, Formula VII, Formula VIII, Formula IX,Formula X, or Formula XIII or a pharmaceutically acceptable saltthereof, is administered in combination or in alternation withtocilizumab or sarilumab. Additional nonlimiting examples ofimmunosuppressant drugs used to treat the overreacting immune systeminclude Janus kinase inhibitors (tofacitinib (Xeljanz)); calcineurininhibitors (cyclosporine (Neoral, Sandimmune, SangCya)), tacrolimus(Astagraf XL, Envarsus XR, Prograf)); mTOR inhibitors (sirolimus(Rapamune), everolimus (Afinitor, Zortress)); and, IMDH inhibitors(azathioprine (Azasan, Imuran), leflunomide (Arava), mycophenolate(CellCept, Myfortic)). Additional antibodies and biologics includeabatacept (Orencia), adalimumab (Humira), anakinra (Kineret),certolizumab (Cimzia), etanercept (Enbrel), golimumab (Simponi),infliximab (Remicade), ixekizumab (Taltz), natalizumab (Tysabri),rituximab (Rituxan), secukinumab (Cosentyx), tocilizumab (Actemra),ustekinumab (Stelara), vedolizumab (Entyvio), basiliximab (Simulect),and daclizumab (Zinbryta)).

IL-1 blocks the production of IL-6 and other proinflammatory cytokines.COVID patients are also sometimes treated with anti-IL-1 therapy toreduce a hyperinflammatory response, for example, an intravenousadministration of anakinra. Anti-IL-1 therapy generally may be forexample, a targeting monoclonal antibody, pharmaceutical inhibitor orprotein degrader such as a bispecific compound that binds to IL-1 andalso to a protein that mediates degradation.

Patients with COVID often develop viral pneumonia, which can lead tobacterial pneumonia. Patients with severe COVID-19 can also be affectedby sepsis or “septic shock”. Treatment for bacterial pneumonia secondaryto COVID or for sepsis includes the administration of antibiotics, forexample a macrolide antibiotic, including azithromycin, clarithromycin,erythromycin, or roxithromycin. Additional antibiotics includeamoxicillin, doxycycline, cephalexin, ciprofloxacin, clindamycin,metronidazole, sulfamethoxazole, trimethoprim, amoxicillin, clavulanate,or levofloxacin. In one embodiment, thus a compound of Formula I,Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII,Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, is administered in combinationor in alternation with an antibiotic, for example, azithromycin. Some ofthese antibiotics such as azithromycin have independentanti-inflammatory properties. Such drugs may be used both asanti-inflammatory agents for COVID patients and have a treatment effecton secondary bacterial infections.

A unique challenge in treating patients infected with COVID-19 is therelatively long-term need for sedation if patients require mechanicalventilation which might last up to or greater than 5, 10 or even 14days. For ongoing pain during this treatment, analgesics can be addedsequentially, and for ongoing anxiety, sedatives can be addedsequentially. Non-limiting examples of analgesics include acetaminophen,ketamine, and PRN opioids (hydromorphone, fentanyl, and morphine).Non-limiting examples of sedatives include melatonin, atypicalantipsychotics with sedative-predominant properties (olanzapine,quetiapine), propofol or dexmedetomidine, haloperidol, andphenobarbital. In one embodiment, a compound of Formula I, Formula II,Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof, is administered in combination or inalternation with a pain reliever, such as acetaminophen, ketamine,hydromorphone, fentanyl, or morphine. In one embodiment, a compound ofFormula I, Formula II, Formula III, Formula IV, Formula V, Formula VI,Formula VII, Formula VIII, Formula IX, Formula X, or Formula XIII or apharmaceutically acceptable salt thereof, is administered in combinationor in alternation with a sedative, such as melatonin, olanzapine,quetiapine, propofol, dexmedetomidine, haloperidol, or phenobarbital.

Investigational drugs for COVID-19 include chloroquine andhydroxychloroquine. In one embodiment, a compound of Formula I, FormulaII, Formula III, Formula IV, Formula V, Formula VI, Formula VII, FormulaVIII, Formula IX, Formula X, or Formula XIII or a pharmaceuticallyacceptable salt thereof, is administered in combination or inalternation with chloroquine or hydroxychloroquine.

A protease inhibitor such as lopinavir or ritonavir, previously approvedfor HIV, may also be administered.

Additional drugs that may be used in the treatment of a COVID patientinclude, but are not limited to favipiravir, fingolimod (Gilenya),methylprednisolone, bevacizumab (Avastin), Actemra (tocilizumab),umifenovir, losartan and the monoclonal antibody combination of REGN3048and REGN3051 or ribavirin. Any of these drugs or vaccines can be used incombination or alternation with an active compound provided herein totreat a viral infection susceptible to such.

In one embodiment, a compound of the present invention is used in aneffective amount in combination with anti-coronavirus vaccine therapy,including but not limited to mRNA-1273 (Moderna, Inc.), AZD-1222(AstraZeneca and University of Oxford), BNT162 (Pfizer and BioNTech),CoronaVac (Sinovac), NVX-CoV 2372 (NovoVax), SCB-2019 (Sanofi and GSK),ZyCoV-D (Zydus Cadila), and CoVaxin (Bharat Biotech). In anotherembodiment, a compound of the present invention is used in an effectiveamount in combination with passive antibody therapy or convalescentplasma therapy.

SARS-CoV-2 is constantly mutating, which many increase virulence andtransmission rates. Drug-resistant variants of viruses may emerge afterprolonged treatment with an antiviral agent. Drug resistance may occurby mutation of a gene that encodes for an enzyme used in viralreplication. The efficacy of a drug against an RNA virus infection incertain cases can be prolonged, augmented, or restored by administeringthe compound in combination or alternation with another, and perhapseven two or three other, antiviral compounds that induce a differentmutation or act through a different pathway, from that of the principledrug.

Alternatively, the pharmacokinetics, bio distribution, half-life, orother parameter of the drug can be altered by such combination therapy(which may include alternation therapy if considered concerted). Sincethe disclosed purine nucleotides are polymerase inhibitors, it may beuseful to administer the compound to a host in combination with, forexample a:

-   -   (1) Protease inhibitor;    -   (2) Another polymerase inhibitor;    -   (3) Allosteric polymerase inhibitor;    -   (4) Interferon alfa-2a, which may be pegylated or otherwise        modified, and/or ribavirin;    -   (5) Non-substrate-based inhibitor;    -   (6) Helicase inhibitor;    -   (7) Antisense oligodeoxynucleotide (S-ODN);    -   (8) Aptamer;    -   (9) Nuclease-resistant ribozyme;    -   (10) iRNA, including microRNA and SiRNA;    -   (11) Antibody, partial antibody or domain antibody to the virus;        or    -   (12) Viral antigen or partial antigen that induces a host        antibody response.

EXAMPLES

General Methods

¹H, ¹⁹F and ³¹P NMR spectra were recorded on a 400 MHz Fourier transformBrücker spectrometer. Spectra were obtained DMSO-d₆ unless statedotherwise. The spin multiplicities are indicated by the symbols s(singlet), d (doublet), t (triplet), m (multiplet) and, br (broad).Coupling constants (J) are reported in Hz. The reactions were generallycarried out under a dry nitrogen atmosphere using Sigma-Aldrichanhydrous solvents. All common chemicals were purchased from commercialsources.

The following abbreviations are used in the Examples:

-   -   BID: Twice a day    -   DCM: Dichloromethane    -   EtOAc: Ethyl acetate    -   EtOH: Ethanol    -   GT: Genotype    -   HPLC: High pressure liquid chromatography    -   LD: Loading dose    -   NaOH: Sodium hydroxide    -   Na₂SO₄: Sodium sulphate (anhydrous)    -   MeOH: Methanol    -   Na₂SO₄: Sodium sulfate    -   NH₄Cl: Ammonium chloride    -   PE: Petroleum ether    -   Silica gel (230 to 400 mesh, Sorbent)    -   t-BuMgCl: t-Butyl magnesium chloride    -   THF: Tetrahydrofuran (THF), anhydrous    -   TP: Triphosphate

Example 1. Synthesis of Compound 1A and Compound 2A Part A: Synthesis of(2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-2-(hydroxymethyl)-4-methyltetrahydrofuran-3-ol(1-7)

In Step 1, Compound 1-1 is dissolved in DCM and the reaction is cooledto 10° C. before benzyl chloroformate is added followed by NEt₃. Thereaction is allowed to cool to room temperature and stir for 12-14hours. Following appropriate work-up and purification conditions,Compound 1-2 is isolated. In Step 2, Compound 1-2 is dissolved inacetonitrile and cooled to −15 to 5° C. before Morpho DAST is added. Thereaction is allowed to stir for 6 hours. Following appropriate work-upand purification conditions, Compound 1-3 is isolated. In Step 3,Compound 1-3 is dissolved in toluene and the reaction is cooled to 0-10°C. before Red Al is added. Following appropriate work-up andpurification conditions, Compound 1-4 is isolated as the diastereomerwith (R)-stereochemistry at the hydroxyl position. In Step 4, Compound1-4 is dissolved in acetonitrile and cooled to −15 to 5° C. before CBr₄and PPh₃ are added. Following appropriate work-up and purificationconditions, Compound 1-5 is isolated. In Step 5, Compound 1-5 isdissolved is acetonitrile and t-BuOH, t-BuOK, and6-chloro-9H-purin-2-amine are added. The reaction is heated to 40-50° C.Following appropriate work-up and purification conditions, Compound 1-6is isolated. In Step 6, Compound 1-6 is dissolved in MeOH and MeNH₂ isadded. The reaction is heated to 20-30 C. Following appropriate work-upand purification conditions, Compound 1-7 is isolated.

Part B: Synthesis of dihydroquinine salt of isopropyl(hydroxy(phenoxy)phosphoryl)-L-alaninate (1-12)

Phenyl dichlorophosphate (1-8, 150 g, 1.0 eq.) was added into 1300 mL ofisopropyl acetate. The solution was cooled to −10° C.±5° C. and then asolution of benzyl alcohol (1-9, 80.6 g, 1.05 eq.) and Et₃N (86.3 g, 1.2eq.) was added. The mixture was stirred for 3 hours at −10±5° C. The endpoint of reaction was monitored by TLC.

L-Alanine isopropyl ester hydrochloride (1-10, 125 g, 1.05 eq.) and Et₃N(152 g, 2.1 eq.) were added at −10° C.±5° C. The reaction mixture wasstirred at −10±5° C. for 2 hours. The end point of reaction wasmonitored by TLC.

The reaction mixture was filtered, and the filter cake was washed with20 mL of isopropyl acetate. The filtrate was washed with 1N HCl, water,and aqueous sodium bicarbonate. The separated organic layer was driedwith anhydrous Na₂SO₄ and then concentrated to dryness under vacuum at40° C.-50° C. to give 240 g of crude product 1-11 as a diastereomericmixture (approximately, 1:1). (Pale yellow oil; yield: 89.6% mol/mol;HPLC purity: 83.4% by area; HPLC assay: 86.2% w/w). The productcontained around 6%-7% residual benzyl alcohol. The crude 1-4 was useddirectly in the next step.

Compound 1-11 (135 g, 1.0 eq., 86.2% assay) and quinine (100 g, 1.0 eq.)were added into 650 mL of i-PrOH. After 5% Pd/C (19.2 g, 60% water byKF) was added, hydrogenation was performed at 20° C.-25° C. for 8 hoursusing a hydrogen bag in a closed system. After completion of reaction,the mixture was filtered through a Buchner funnel. The filtrate wasconcentrated under vacuum to remove the solvent.

To the above residue, 300 mL of TBME was added. The mixture wasconcentrated to remove the solvent under vacuum at 40° C.-45° C., andthen this step was repeated with another 300 mL of MTBE. To the above,600 mL of MTBE was added, and the mixture was stirred at 40° C.-45° C.for 1 hour and then stirred at 0° C.-5° C. for additional 1 hour. Themixture was filtered, and the filter cake was washed with 100 mL ofMTBE. The cake was dried at 45° C. for 16 hours without vacuum to give152 g of the dihydroquinine salt of isopropyl(hydroxy(phenoxy)phosphoryl)-L-alaninate (1-12, white solid; yield:69.5% mol/mol; HPLC Purity: 97.91%).

Part C: Synthesis of Compound 1A

The dihydroquinine salt of isopropyl(hydroxy(phenoxy)phosphoryl)-L-alaninate (1-12, 5.9 g, 1.5 eq.),Compound 1-7 (2.0 g, 1.0 eq), DIPEA (0.83 g, 1.0 eq), and HATU (3.65 g,1.5 eq) were added into 100 mL of dichloromethane. The mixture washeated to 40° C. and stirred for 18 hours. The reaction was monitored byTLC and HPLC.

After the reaction was completed, the reaction mixture was cooled toroom temperature, washed with 1N hydrochloric acid (100 mL×2), water(100 mL×2), and 5% aqueous sodium bicarbonate 15 mL×1). The separatedorganic phase was dried with 2 g of anhydrous sodium sulfate, filtered,and concentrated at 40° C.-45° C. under vacuum to give a yellow oil.

Isopropyl acetate (10 mL of) was added. After stirring, the mixture wasconcentrated under vacuum. Then, 25 mL of isopropyl acetate was added.The mixture was heated to 45° C. to afford a clear solution. Afterstirring at room temperature for 2 hours, the solid precipitate wasfiltered and dried without vacuum at 45° C. for 15 hours to give 2.0 gof crude Compound 1A (yield: 53.8% mol/mol; HPLC purity: 93.1% by area(containing 3.7% of R_(p)-Compound 1B).

The mixture of crude Compound 1A (2.0 g) and 15 mL of isopropyl acetatewas heated to 80° C.-85° C. to afford a solution. The solution wascooled to 20° C.-25° C. and stirred for 1 hour. The precipitated solidwas filtered, washed with isopropyl acetate (1 mL), and dried withoutvacuum at 50° C. for 16 hours to give 1.7 g of Compound 1A (yield: 45.7%mol/mol; HPLC purity: 98.99%). ¹H NMR, ¹⁹F NMR, and ³¹P NMR spectraconfirmed the structure of Compound 1A.

Part D. Synthesis of Hemi-Sulfate Salt Compound 2A

A 250 mL flask was charged with MeOH (151 mL) and the solution wascooled to 0-5° C. A concentrated solution of H₂SO₄ was added dropwiseover 10 minutes. A separate flask was charged with Compound 1A (151 g)and acetone (910 mL), and the H₂SO₄/MeOH solution was added dropwise at25-30° C. over 2.5 hours. A large amount of solid was precipitated.After the solution was stirred for 12-15 hours at 25-30° C., the mixturewas filtered, washed with MeOH/acetone (25 mL/150 mL), and dried at55-60° C. in vacuum to afford Compound 2A (121 g, 74%). ¹HNMR: (400 MHz,DMSO-d₆): δ 8.41 (br, 1H), 7.97 (s, 1H), 7.36 (t, J=8.0 Hz, 2H), 7.22(d, J=8.0 Hz, 2H), 7.17 (t, J=8.0 Hz, 1H), 6.73 (s, 2H), 6.07 (d, J=8.0Hz, 1H), 6.00 (dd, J=12.0, 8.0 Hz, 1H), 5.81 (br, 1H), 4.84-4.73 (m,1H), 4.44-4.28 (m, 3H), 4.10 (t, J=8.0 Hz, 2H), 3.85-3.74 (m, 1H), 2.95(s, 3H), 1.21 (s, J=4.0 Hz, 3H), 1.15-1.10 (m, 9H).

Example 2. Synthesis of Select Compounds of the Present Invention

NMR spectra were recorded on a 400 MHz Fourier transform Brückerspectrometer. Spectra were obtained from samples prepared in 5 mmdiameter tubes in CDCl₃, CD₃OD or DMSO-d6. The spin multiplicities areindicated by the symbols s (singlet), d (doublet), t (triplet), m(multiplet) and, br (broad). Coupling constants (J) are reported in Hz.MS spectra were obtained using electrospray ionisation (ESI) on anAgilent Technologies 6120 quadrupole MS apparatus. The reactions weregenerally carried out under a dry nitrogen atmosphere usingSigma-Aldrich anhydrous solvents. All common chemicals were purchasedfrom commercial sources.

Synthesis 2. Isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(Compound 5)

Step 1:N-(6-Chloro-9-((6aR,8R,9R,9aR)-2,2,4,4-tetraisopropyl-9-((trimethylsilyl)oxy)tetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)acetamide:A solution of intermediate 2-1 (50.2 g, 92.25 mmol) in DCM (500 mL) andpyridine (75 ml) was added TMSCl (30.1 g, 276.74 mmol) at 0° C. andstirred for 0.5 h at 0° C. To the solution was added acetic anhydride(28.2 g, 276.74 mmol) and the reaction was stirred for 0.5 h at 0° C.and then at room temperature for 1 hour. To the reaction mixture wasadded H₂O and EtOAc. The organic phase was washed with saturated brine,dried over anhydrous Na₂SO₄, and concentrated. The residue was purifiedby column chromatography (silica gel, EA/PE=0 to 10%) to affordintermediate 2-2 (53 g, 51%) as a yellow solid.

Step 2:N-(6-Chloro-9-((6aR,8R,9R,9aS)-9-hydroxy-2,2,4,4-tetraisopropyltetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)acetamide:To a solution of intermediate 2-2 (53 g, 82.25 mmol) in THE (530 mL) wasadded p-toluenesulfonic acid monohydrate (5.9 g, 36.67 mmol) at roomtemperature. The solution was stirred for 1 h at room temperature. Then,TEA (8.3 g, 82.25 mmol) was added and the reaction mixture wasconcentrated. The residue was purified by column chromatography (silicagel, EA/PE=10% to 20%) to afford intermediate 2-3 (47 g, 99.5%) as awhite solid.

Step 3:N-(6-Chloro-9-((6aR,8R,9aR)-2,2,4,4-tetraisopropyl-9-oxotetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)acetamide:Chromium trioxide (18.9 g, 189.36 mmol) was dispersed in DCM (280 mL),and pyridine (15.0 g, 189.36 mmol) and acetic anhydride (19.3 g, 189.36mmol) were added dropwise. The reaction mixture turned black.Intermediate 2-3 (37 g, 63.12 mmol) in DCM (380 ml) was added at roomtemperature and the reaction was stirred for 0.5 h. EtOAc (1200 mL) wasadded. The reaction mixture was filtered and concentrated, azeotropicwith toluene (200 mL). The residue was purified by column chromatography(silica gel, EA/PE=33% to 100%) to afford intermediate 2-4 (34.8 g, 94%)as a white solid.

Step 4:N-(6-Chloro-9-((6aR,8R,9S,9aR)-9-hydroxy-2,2,4,4-tetraisopropyl-9-methyltetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)acetamide:Magnesium chips (6.7 g, 278.66 mmol) were dispersed in anhydrous ether(380 mL), deuterated methyl iodide (9.2 g, 63.33 mmol) was added, andthe reaction was stirred for 0.5 h at room temperature before beingbrought to room temperature. Deuterated methyl iodide (27.5 g, 190.00mmol) was added dropwise, and the reaction was stirred for 1 h beforebeing brought to below 10° C. and adding intermediate 2-4 (37 g, 63.33mmol) in DCM (380 ml). The reaction was stirred for 1 hour and thenquenched by saturated NaHCO₃ and extracted with EtOAc. The organic phasewas washed with saturated brine, dried over anhydrous Na₂SO₄, andconcentrated. The residue was purified by column chromatography (silicagel, EA/PE=33% to 50%) to afford intermediate 2-5 (22 g, 57.9%) as asolid.

Step 5:N-(6-Chloro-9-((2R,3S,4R,5R)-3,4-dihydroxy-5-(hydroxymethyl)-3-methyltetrahydrofuran-2-yl)-9H-purin-2-yl)acetamide:To a solution of intermediate 2-5 (22 g, 36.65 mmol) in THE (150 mL) wasadded tetrabutylammonium fluoride (23.12 g, 73.30 mmol) in THE (70 ml).The solution was stirred for 1 h at room temperature and concentrated.The residue was purified by column chromatography (silica gel,MeOH/DCM=2% to 5%) to afford intermediate 2-6 (20 g, >100%) as a solid.

Step 6:(2R,3R,4S,5R)-5-(2-Acetamido-6-chloro-9H-purin-9-yl)-2-(acetoxymethyl)-4-hydroxy-4-methyltetrahydrofuran-3-ylacetate: To a solution of intermediate 2-6 (20 g, 55.90 mmol) in dry DCM(400 mL) and pyridine (8 ml) was added acetic anhydride (22.8 g, 223.62mmol). The solution was stirred overnight at 0° C. Then, EtOAc was addedand the suspension was filtered. The solution was washed brine, driedover anhydrous Na₂SO₄ and concentrated. The residue was purified bycolumn chromatography to afford intermediate 2-7 (8.4 g, 29.8% yieldover 3 steps) as a solid.

Step 7:(2R,3R,4R,5R)-5-(2-Acetamido-6-chloro-9H-purin-9-yl)-2-(acetoxymethyl)-4-fluoro-4-methyltetrahydrofuran-3-ylacetate: To a solution of intermediate 2-7 (5.4 g, 12.22 mmol) in DCM(220 mL) was added DAST (5.9 g, 36.67 mmol) dropwise at −65° C. and thereaction was stirred for 0.5 h. The reaction was allowed to warm to roomtemperature and stirred for 1 hours. The reaction was quenched bysaturated NaHCO₃ and separated. The organic phase was washed withsaturated brine, dried over anhydrous Na₂SO₄, and concentrated. Theresidue was purified by column chromatography (silica gel, EA/PE=50% to100%) to afford intermediate 2-8 (1.54 g, 30%) as a solid.

Step 8:(2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-2-(hydroxymethyl)-4-methyltetrahydrofuran-3-ol:A solution of intermediate 2-8 (890 mg, 2.01 mmol) in methylamine (18%in EtOH) (36 mL) in a sealed container was stirred overnight at roomtemperature and concentrated. Additional sodium methoxide (325.0 mg,6.02 mmol) was then added before the solution stirred for 1 additionalhour at RT. Acetic acid was added to adjust to pH of 7 and the solutionwas concentrated. The residue was purified by column chromatography(silica gel, MeOH/DCM=0 to 2%) to afford intermediate 2-9 (400 mg,64.5%) as a solid. ¹H NMR (400 MHz, CD₃OD) δ8.057 (s, 1H), 6.103 (d,J=18.4 Hz, 1H), 4.047-4.015 (m, 2H), 3.878-3.845 (m, 1H), 3.030 (s, 3H).¹⁹F NMR (400 MHz, CD₃OD) δ 164.351 (s). MS (ESI) m/z calcd. forC₁₂H₁₄D₃FN₆O₃ [M+H]⁺ 316.13. found 316.4.

Step 9:Isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate:To a solution of intermediate 2-9 (230 mg, 0.736 mmol) and isopropyl((R)-(perfluorophenoxy)(phenoxy)phosphoryl)-L-alaninate (334 mg, 0.736mmol) in THE (4 ml) was added t-BuMgCl (1.7 N in THF) (912 μL, 1.55mmol) dropwise at −5° C. The solution stirred for 0.5 h at 0° C. Thereaction mixture was then quenched by saturated NH₄Cl aqueous solution.The residue was purified by column chromatography (silica gel,MeOH/DCM=0 to 3.3%) to afford Compound 5 (130 mg, 30.5%) as a solid. ¹HNMR (400 MHz, DMSO) δ 7.81 (s, 1H), 7.32-7.16 (m, 5H), 6.13-6.08 (d,J=18.8, 8.0 Hz, 1H), 4.87 (s, 1H), 4.50 (m, 3H), 4.19 (m, 1H), 3.89 (m,1H), 3.02 (s, 1H), 1.30-1.27 (m, 3H), 1.17-1.13 (m, 9H). ¹⁹F NMR (400MHz, DMSO) δ −163.42 (s). MS (ESI) m/z calcd. for C₂₄H₃₀D₃FN₇O₇P [M+H]⁺585.22. found 585.5.

Synthesis 3. Isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-4-(fluoromethyl)-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(Compound 6)

Step 1:(6aR,8R,9R,9aS)-8-(2-Amino-6-chloro-9H-purin-9-yl)-2,2,4,4-tetraisopropyltetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-9-ol:To a solution of intermediate 3-1 (81.8 g, 0.27 mol) in pyridine (330mL) was added TPDSCl₂ (102.6 g, 0.32 mol) drop-wise at 0±5° C. Thesolution was stirred for 2h at 0° C. and quenched by water. Then, EtOAcwas added, and the phases were separated and dried over anhydrousNa₂SO₄. The solution was concentrated and azeotropic with toluene threetimes to remove the pyridine. The residue was purified by columnchromatography (DCM/MeOH=200:1-100:1) to afford intermediate 3-2 (123.3g, 83.6% yield) as an oil.

Step 2:N-(6-Chloro-9-((6aR,8R,9R,9aR)-2,2,4,4-tetraisopropyl-9-((trimethylsilyl)oxy)tetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)isobutyramide:To a solution of intermediate 3-2 (122.6 g 0.225 mol) in DCM (1300 mL)and pyridine (184 mL) was added TMSCl (48.7 g, 0.45 mol) drop-wise at0-5° C. The reaction mixture was stirred for 10 min at 0° C. Then,Isobutyryl chloride (36 g, 0.337 mol) was added and the reaction wasstirred for another 10 minutes at 0° C. Water was added, and the phaseswere separated and washed with CuSO₄ aqueous solution. The organic phasewas washed with brine, dried over anhydrous Na₂SO₄ and concentrated toobtain the crude intermediate 3-3 (151.7 g).

Step 3:N-(6-Chloro-9-((6aR,8R,9R,9aS)-9-hydroxy-2,2,4,4-tetraisopropyltetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)isobutyramide:To a solution of intermediate 3-3 (151.7 g, 0.22 mol) in THE (1500 mL)was added p-toluenesulfonic acid monohydrate (29 g, 0.155 mol). Themixture was stirred at room temperature for 10 minutes and then quenchedby addition of triethylamine (35 ml). The solution was concentrated andpurified by column chromatography (DCM/MeOH=200:1-100:1) to obtain theintermediate 3-4 (81 g, 58.5% yield over 2 steps).

Step 4:N-(6-Chloro-9-((6aR,8R,9aR)-2,2,4,4-tetraisopropyl-9-oxotetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)isobutyramide:To a solution of intermediate 3-4 (40 g, 0.065 mol) in DCM (300 mL) wasadded DMP (56 g, 0.13 mol) at 0° C. The reaction mixture was stirred atroom temperature overnight. Then, ether (2000 mL) was added and thesuspension was filtered. The solution was washed with saturated NaHCO₃aqueous solution, saturated Na₂S₂O₃ aqueous solution and brinesuccessively. The organic phase was dried over anhydrous Na₂SO₄,concentrated and azeotropic with toluene to obtain the intermediate 3-5,which was used in the next step directly.

Step 5:N-(6-Chloro-9-((6aR,8R,9S,9aR)-9-hydroxy-2,2,4,4-tetraisopropyl-9-((trimethylsilyl)ethynyl)tetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)isobutyramide:To a solution of trimethylsilylacetylene (52 g, 0.529 mol) in dry THE(350 ml) was added n-butyllithium (204 ml, 0.51 mol) drop-wise at−15˜−20° C. The solution was stirred for 30 mins at −15˜−20° C. Then,the reaction mixture was cooled down to −70° C. and a solution ofintermediate 3-5 (54 g, 0.088 mol) in dry DMF (200 mL) was addeddrop-wise. The solution was stirred for 20 mins at −70° C. The resultingsolution was slowly warmed up to 0° C. and quenched by addition ofsaturated NH₄Cl aqueous solution. EtOAc was added, the organic phaseswere separated and washed with brine, dried over anhydrous Na₂SO₄ andconcentrated. The residue was purified by column chromatography(DCM/MeOH=200:1-100:1) to afford intermediate 3-6 (35.1 g, 56% yieldover 2 steps) as a yellow solid.

Step 6:N-(6-Chloro-9-((6aR,8R,9R,9aR)-9-fluoro-2,2,4,4-tetraisopropyl-9-((trimethylsilyl)ethynyl)tetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-9H-purin-2-yl)isobutyramide:To a solution of intermediate 3-6 (2 g, 2.81 mmol) in DCM (20 mL) andpyridine (0.703 g, 8.85 mmol) was added DAST (2.27 g, 14.05 mmol) at−70° C. The reaction mixture was slowly warmed up to −30° C. and stirredfor 5 mins at −30° C. Then, the solution was added into the saturatedNaHCO₃ aqueous solution slowly and DCM was added. The organic phaseswere separated and washed with brine, dried over anhydrous Na₂SO₄ andconcentrated. The residue was purified by column chromatography(DCM/MeOH=200:1-100:1) to afford intermediate 3-7 (1.257 g, 62.85%yield) as a white solid.

Step 7:N-(9-((6aR,8R,9R,9aR)-9-Ethynyl-9-fluoro-2,2,4,4-tetraisopropyltetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-6-(methylamino)-9H-purin-2-yl)isobutyramide:To a solution of intermediate 3-7 (14 g, 19.65 mmol) in methanol (30 mL)was added 30% methylamine methanol solution (30 ml) at 0° C. and thereaction was stirred at room temperature for min. The solution was thenconcentrated to remove the methylamine at RT. Then, the resultingsolution was concentrated and purified by column chromatography(DCM/MeOH=200:1-100:1) to afford intermediate 3-8 (8.8 g, 70.4% yield)as a white solid.

Step 8:N-(9-((6aR,8R,9R,9aR)-9-Fluoro-2,2,4,4-tetraisopropyl-9-vinyltetrahydro-6H-furo[3,2-f][1,3,5,2,4]trioxadisilocin-8-yl)-6-(methylamino)-9H-purin-2-yl)isobutyramide.To a solution of intermediate 3-8 (8.8 g, 13.86 mmol) in EtOAc (88 mL)was added Lindlar catalyst (3.52 g). Then, the solution was stirredovernight under hydrogen atmosphere (0.8 MPa) at RT. The reactionmixture was filtered to remove the catalyst, concentrated, and purifiedby column chromatography (DCM/MeOH=200:1-100:1) to afford intermediate3-9 (7.5 g, 85.2% yield) as a solid.

Step 9:N-(9-((2R,3R,4R,5R)-3-Fluoro-4-hydroxy-5-(hydroxymethyl)-3-vinyltetrahydrofuran-2-yl)-6-(methylamino)-9H-purin-2-yl)isobutyramide.To a solution of intermediate 3-9 (7.5 g, 11.77 mmol) in THE (40 ml) wasadded the solution of TBAF (5.56 g, 17.65 mmol) in THE (35 ml) at 0° C.When TLC indicated complete conversion of the starting material, thesolution was concentrated and purified by column chromatography(DCM/MeOH=200:1-10:1) to afford intermediate 3-10 (3.8 g, 82.6% yield)as a solid.

Step 10:((2R,3R,4R,5R)-3-(Benzoyloxy)-4-fluoro-5-(2-isobutyramido-6-(methylamino)-9H-purin-9-yl)-4-vinyltetrahydrofuran-2-yl)methylbenzoate. To a solution of compound intermediate 3-10 (3.7 g, 9.38 mmol)in pyridine (19 ml) was added BzCl (2.9 g, 20.64 mmol) at 0° C. Thereaction mixture was stirred overnight at RT. Then, the reaction mixturewas quenched by methanol and concentrated. The residue was purified bycolumn chromatography (DCM/MeOH=200:1-100:1) to afford intermediate 3-11(4.68 g, 82.8% yield) as a white solid.

Step 11:((2R,3R,4R,5R)-3-(Benzoyloxy)-4-((S)-1,2-dihydroxyethyl)-4-fluoro-5-(2-isobutyramido-6-(methylamino)-9H-purin-9-yl)tetrahydrofuran-2-yl)methylbenzoate. To a solution of intermediate 3-11 (4.68 g, 7.77 mmol) in THE(46.8 ml) and H₂O (9.36 ml) was added NMO (1.82 g, 15.53 mmol) and OsO₄(0.65 g, 2.56 mmol. The reaction mixture was stirred overnight at RT.Then, the reaction mixture was quenched by saturated Na₂S₂O₃ aqueoussolution and EtOAc was added. The organic phases were separated andwashed with brine, dried over anhydrous Na₂SO₄ and concentrated. Theresidue was purified by column chromatography (DCM/MeOH=200:1-50:1) toafford intermediate 3-12 (4 g, 82% yield) as a white solid.

Step 12:((2R,3R,4R,5R)-3-(Benzoyloxy)-4-fluoro-4-(hydroxymethyl)-5-(2-isobutyramido-6-(methylamino)-9H-purin-9-yl)tetrahydrofuran-2-yl)methylbenzoate. Intermediate 3-12 (4 g, 6.28 mmol) was dissolved in methanol(40 ml), THE (11.7 ml) and water (7 ml). Then, sodium metaperiodate (2g, 9.42 mmol) was added to the solution and reaction mixture was stirredfor 3h at RT. The reaction mixture was filtered and washed with methanoland THF. NaBH₄ (0.382 g, 10.05 mmol) was added to the resulting solutionin portions and the reaction was stirred for 10 minutes. The reactionmixture was quenched by ice water and EtOAc was added. The organicphases were separated and washed with brine, dried over anhydrous Na₂SO₄and concentrated. The residue was purified by column chromatography(DCM/MeOH=200:1-50:1) to afford intermediate 3-13 (3.17 g, 83.2% yield)as a white solid.

Step 13:((2R,3R,4R,5R)-3-(Benzoyloxy)-4-fluoro-4-(fluoromethyl)-5-(2-isobutyramido-6-(methylamino)-9H-purin-9-yl)tetrahydrofuran-2-yl)methylbenzoate. To a solution of intermediate 3-13 (1000 mg, 1.65 mmol) in DCM(10 ml) and pyridine (650 mg, 8.24 mmol) was addedtrifluoromethanesulfonic anhydride (838 mg, 2.97 mmol) at −15˜−20° C.The reaction mixture was stirred for 10 min at −15˜−20° C. The solutionwas quenched by saturated NaHCO₃ aqueous solution and washed with CuSO₄aqueous solution. Then, the organic phase was washed with brine, driedover anhydrous Na₂SO₄ and concentrated. The crude product was dissolvedin acetonitrile (10 ml) and TBAF (1M, 8.25 ml) in THE was added to theresulting solution. The reaction mixture was stirred for 5 min andmonitored by TLC. The reaction was then diluted with EtOAc and water.The phases were separated and washed with brine, dried over anhydrousNa₂SO₄ and concentrated. The residue was purified by columnchromatography (DCM/MeOH=200:1-100:1) to afford intermediate 3-14 (113mg, 37.7% yield) as a white solid.

Step 14:(2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-4-(fluoromethyl)-2-(hydroxymethyl)tetrahydrofuran-3-ol.Intermediate 3-14 (0.51 g, 0.84 mmol) was dissolved in 20% methylaminemethanol solution and stirred overnight at 100° C. in a sealed steelreactor. The reaction mixture was concentrated and purified by columnchromatography (DCM/MeOH=200:1-10:1) to afford intermediate 3-15 (241mg, 87.6% yield) as a white solid. ¹H NMR (400 MHz, CD₃OD) δ 7.94 (s,1H), 6.28 (d, J=20.0 Hz, 1H), 4.84-4.56 (m, 1H), 4.46 (t, J=24.0 Hz,1H), 4.35-3.89 (m, 1H), 3.86 (m, 2H), 3.30 (d, J=20.0 Hz, 1H), 3.03 (s,3H). ¹⁹F NMR (400 MHz, CD₃OD) δ 179.67 (s), 80.15 (s).

Step 15:Isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-4-(fluoromethyl)-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate.Intermediate 3-15 (150 mg, 0.45 mmol) was dissolved in acetonitrile (6mL), NMI (895.6 mg, 10.80 mmol) was added at RT. The solution was cooleddown to 0° C. and a solution of isopropyl(chloro(phenoxy)phosphoryl)-L-alaninate (1247.7 mg, 4.05 mmol) inacetonitrile (2 mL) was added drop-wise. The reaction mixture wasstirred at 0° C. for 5 min and monitored by TLC. Then, the resultingsolution was quenched by water and diluted with EtOAc. The phases wereseparated and washed with brine, dried over anhydrous Na₂SO₄ andconcentrated. The residue was purified by column chromatography(DCM/MeOH=200:1-30:1) to afford Compound 6 (111 mg, 40.8% yield) wasobtained as a white solid.

¹H NMR (400 MHz, CD₃OD) δ 7.78 (s, 1H), 7.31-7.16 (m, 5H), 6.27 (dd,J=20.0, 8.0 Hz, 1H), 4.91-4.84 (m, 1H), 4.56 (m, 1H), 4.51 (m, 4H), 4.50(m, 1H), 3.87 (dd, J=20.0, 8.0 Hz, 1H), 3.03 (s, 3H), 1.27-1.13 (m, 9H).¹⁹F NMR (400 MHz, CD₃OD) δ 179.09 (s). ³¹P NMR (400 MHz, CD₃OD) δ 3.86,3.79 (d). MS (ESI) m/z calcd. for C₂₄H₃₂F₂N₇O₇P [M+H]⁺ 600.2. found600.2.

Synthesis 4. Isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-ethynyl-4-fluoro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(Compound 7)

Step 1: To a solution of intermediate 4-1 (30 mg, 0.09 mmol) in dry THF(2 mL) was added tert-butylmagnesium chloride (1 M in THF) (112 μL, 0.11mmol) drop-wise at 0° C. The solution was stirred for 15 mins at 0° C.and for 45 mins at RT. Then, the reaction mixture was cooled down to 0°C. and a solution of isopropyl((R,S)-(pentafluorophenoxy)-phenoxy-phosphoryl)-L-alaninate (51 mg, 0.11mmol) in dry THE (1 mL) was added drop-wise. The resulting solution wasslowly warmed up to room temperature and stirred for 15 h. The reactionmixture was then diluted with EtOAc (10 mL) and saturated NH₄Cl aqueoussolution (8 mL). The phases were separated and the aqueous layer wasback-extracted with EtOAc (2×5 mL). The combined organics were washedwith saturated NH₄Cl aqueous solution (10 mL) and brine (10 mL), driedover Na₂SO₄ and concentrated. The residue was purified by columnchromatography (silica gel, DCM/MeOH 0 to 10%) and by reverse phasecolumn chromatography (C-18 silica, H₂O/MeOH 0 to 100%).

Compound 7 (9 mg, 16%) was obtained as a white solid. ¹H NMR (300 MHz,CD₃OD) δ 7.81, 7.79 (s+s, 1H), 7.36-7.14 (m, 5H), 6.26 (d, J=17.4 Hz,0.1H), 6.24 (d, J=17.4 Hz, 0.9H), 4.93-4.89 (overlapped with H₂O, m,1H), 4.80-4.78 (m, 1H), 4.53-4.49 (m, 2H), 4.21-4.18 (m, 1H), 3.95-3.84(m, 1H), 3.23-3.20 (m, 1H), 3.04 (bs, 1H), 1.31-1.14 (m, 9H). ³¹P NMR(121 MHz, CD₃OD) δ 4.06 (s), 3.97 (s). MS (ESI) m/z calcd. forC₂₅H₃₂FN₇O₇P [M+H]⁺ 592.2. found 592.2.

Synthesis 5. Isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-vinyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(Compound 8)

Step 1:(2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-2-(hydroxymethyl)-4-vinyltetrahydrofuran-3-ol(3). To a solution of intermediate 4-1 (255 mg, 0.79 mmol) in EtOH (4mL) was added palladium (5% on BaSO₄) (60 mg) and quinoline (2 drops).The solution was put under an atmosphere of H₂ and stirred for 1 h atRT. Then, the mixture was filtered on Celite and concentrated. Theresidue was purified by column chromatography (silica gel, DCM/MeOH 0 to10%). Intermediate 5-1 (177 mg, 70%) was obtained as a white solid. ¹HNMR (400 MHz, CD₃OD) δ 7.98 (s, 1H), 6.12 (d, J=18.6 Hz, 1H), 5.52-5.35(m, 2H), 5.25-5.19 (m, 1H), 4.86-4.70 (m, 1H, overlapped with H₂O),4.13-3.86 (m, 3H), 3.03 (br. s, 3H). MS (ESI) m/z calcd. forC₁₃H₁₈FN₆O₃[M+H]⁺ 325.1. found 325.2.

Step 2: (2S)-Isopropyl2-(((((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-vinyl-4-fluoro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)amino)propanoate. To a solution of intermediate 5-1 (150 mg, 0.47 mmol) in dryTHE (10 mL) was added tert-butylmagnesium chloride (1 M in THF) (560 μL,0.55 mmol) drop-wise at 0° C. The solution was stirred for 15 mins at 0°C. and for 45 mins at RT. Then, the reaction mixture was cooled down to0° C. and a solution of isopropyl((R,S)-(pentafluorophenoxy)-phenoxy-phosphoryl)-L-alaninate (250 mg,0.55 mmol) in dry THE (5 mL) was added drop-wise. The resulting solutionwas slowly warmed up to room temperature and stirred for 15 h. Thereaction mixture was then diluted with EtOAc (50 mL) and saturated NH₄Claqueous solution (40 mL). The phases were separated and the aqueouslayer was back-extracted with EtOAc (2×25 mL). The combined organicswere washed with saturated NH₄Cl aqueous solution (50 mL) and brine (50mL), dried over Na₂SO₄ and concentrated. The residue was purified bycolumn chromatography (silica gel, DCM/MeOH 0 to 10%) and by reversephase column chromatography (C-18 silica, H₂O/MeOH 0 to 100%). Compound8 (45 mg, 16%) was obtained as a white solid. ¹H NMR (400 MHz, CD₃OD) δ7.81 (s, 1H), 7.36-7.14 (m, 5H), 6.12 (d, J=19.1 Hz, 1H), 5.54-5.547 (m,2H), 5.28-5.23 (m, 1H), 4.91-4.81 (m, 1H, overlapped with H₂O),4.58-4.47 (m, 2H), 4.28-4.22 (m, 1H), 3.95-3.85 (m, 1H), 3.05 (br. s,3H), 1.32-1.13 (m, 9H). ³¹P NMR (162 MHz, CD₃OD) δ 3.86 (s). MS (ESI)m/z calcd. for C₂₅H₃₄FN₇O₇P [M+H]⁺ 594.2. found 594.2.

Synthesis 6. Isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-(hydroxymethyl)tetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(Compound 9)

Step 1:(2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-2-(((tert-butyldiphenylsilyl)oxy)methyl)-4-fluoro-4-vinyltetrahydrofuran-3-ol (5). To a solution ofintermediate 5-1 (185 mg, 0.57 mmol) in dry DMF (7 mL) was addedimidazole (232 mg, 3.40 mmol) and TDPSCl (445 μL, 1.70 mmol) at 0° C.The solution was stirred for 1 h at 0° C. The reaction mixture was thendiluted with EtOAc (50 mL) and saturated NH₄Cl aqueous solution (40 mL).The phases were separated and the organic layer was washed withsaturated NH₄Cl aqueous solution (4×30 mL), dried over Na₂SO₄ andconcentrated. The residue was purified by column chromatography (silicagel, DCM/MeOH 0 to 5%) to afford intermediate 6-1 (352 mg, 84%) as awhite solid.

Step 2:(2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-2-(((tert-butyldiphenylsilyl)oxy)methyl)-4-fluoro-4-(hydroxymethyl)tetrahydrofuran-3-ol (6). To asolution of intermediate 6-1 (200 mg, 0.36 mmol) in dioxane (5 mL) wasadded N-methylmorpholine-N-oxide (220 mg, 1.87 mmol) and OsO₄ (4% inH₂O) (210 μL). The solution was stirred for 15 h at room temperature inthe dark. Then, the mixture was diluted with EtOAc (25 mL) and filteredon Celite. The solution was washed brine (20 mL), dried over Na₂SO₄ andconcentrated. The residue was dissolved in DCM (5 mL) and added on NaIO₄(adsorbed on silica) (2.3 g). The resulting slurry was triturated for 15h at RT. Then, the silica was filtered and washed thoroughly with DCM.The combined filtrates were concentrated. The residue was dissolved inEtOH (5 mL) and NaBH₄ (225 mg, 6.0 mmol) was added at 0° C. The solutionwas stirred for 3 h at 0° C. and then quenched with saturated NH₄Claqueous solution (15 mL). The mixture was extracted with EtOAc (2×20mL). The combined organics were washed with brine (10 mL), dried overNa₂SO₄ and concentrated. The residue was purified by columnchromatography (silica gel, DCM/MeOH 0 to 5%) to afford intermediate 6-2(143 mg, 70%) as a white solid.

Step 3:9-((2R,3R,4R,5R)-5-(((tert-Butyldiphenylsilyl)oxy)methyl)-3-fluoro-4-((tetrahydro-2H-pyran-2-yl)oxy)-3-(((tetrahydro-2H-pyran-2-yl)oxy)methyl)tetrahydrofuran-2-yl)-N⁶-methyl-9H-purine-2,6-diamine(7). To a solution of intermediate 6-2 (130 mg, 0.23 mmol) in dry DCM(10 mL) was added 3,4-dihydro-2H-pyran (360 μL, 4.0 mmol) andcamphorsulfonic acid (100 mg, 0.43 mmol). The solution was stirred for 2h at room temperature and diluted with DCM (20 mL). Saturated NaHCO₃aqueous solution (20 mL) was added and the phases were separated. Theorganics were washed with brine (20 mL), dried over Na₂SO₄ andconcentrated. The residue was purified by column chromatography (silicagel, PE/EtOAc 0 to 40%) to afford intermediate 6-3 (137 mg, 81%) as awhite solid.

Step 4:((2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-((tetrahydro-2H-pyran-2-yl)oxy)-4-(((tetrahydro-2H-pyran-2-yl)oxy)methyl)tetrahydrofuran-2-yl)methanol(8). To a solution of intermediate 6-3 (130 mg, 0.18 mmol) in dry THE (5mL) was added TBAF (1 M in THF) (360 μL, 0.36 mmol). The solution wasstirred for 1 h at room temperature and concentrated. The residue waspurified by column chromatography (silica gel, DCM/MeOH 0 to 5%) toafford intermediate 6-4 (81 mg, 92%) as a white solid.

Step 5: (2S)-Isopropyl2-(((((2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-(hydroxymethyl)tetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)amino) propanoate (9). To a solution of intermediate 6-4 (50 mg, 0.10mmol) in dry THE (3 mL) was added tert-butylmagnesium chloride (1 M inTHF) (130 μL, 0.13 mmol) drop-wise at 0° C. The solution was stirred for15 mins at 0° C. and for 45 mins at RT. Then, the reaction mixture wascooled down to 0° C. and a solution of isopropyl((R,S)-(pentafluorophenoxy)-phenoxy-phosphoryl)-L-alaninate (52 mg, 0.11mmol) in dry THE (1 mL) was added drop-wise. The resulting solution wasslowly warmed up to room temperature and stirred for 15 h. The reactionmixture was then diluted with EtOAc (10 mL) and saturated NH₄Cl aqueoussolution (8 mL). The phases were separated and the aqueous layer wasback-extracted with EtOAc (2×5 mL). The combined organics were washedwith saturated NH₄Cl aqueous solution (10 mL) and brine (10 mL), driedover Na₂SO₄ and concentrated. The residue was dissolved in HCl (1.25 Min i-PrOH) (2 mL). The solution was stirred for 2 h at room temperatureand concentrated. The residue was purified by column chromatography(silica gel, DCM/MeOH 0 to 10%) and by reverse phase columnchromatography (C-18 silica, H₂O/MeOH 0 to 100%). Compound 9 (29 mg,49%) was obtained as a white solid. ¹H NMR (400 MHz, CD₃OD) δ 7.80 (s,1H), 7.36-7.13 (m, 5H), 6.17 (d, J=18.3 Hz, 1H), 4.92-4.73 (m, 2H,overlapped with H₂O), 4.55-4.49 (m, 2H), 4.26-4.18 (m, 1H), 3.93-3.80(m, 2H), 3.57-3.43 (m, 1H), 3.03 (br. s, 3H), 1.28 (d, J=7.3 Hz, 3H),1.15 (t, J=6.6 Hz, 6H). ³¹P NMR (162 MHz, CD₃OD) δ 3.90 (s). MS (ESI)m/z calcd. for C₂₄H₃₄FN₇O₈P [M+H]⁺ 598.2. found 598.2.

Synthesis 7. Isopropyl((((2R,3R,4R,5R)-5-(2-amino-6-(cyclopropylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-(hydroxymethyl)tetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(Compound 10)

Step 1:(2R,3R,4R,5R)-5-(2-Amino-6-(cyclopropylamino)-9H-purin-9-yl)-4-fluoro-2-(hydroxymethyl)-4-vinyltetrahydrofuran-3-ol(11). To a solution of intermediate 7-1 (232 mg, 0.67 mmol) in EtOH (4mL) was added palladium (5% on BaSO₄) (50 mg) and quinoline (2 drops).The solution was put under an atmosphere of H₂ and stirred for 1 h atRT. Then, the mixture was filtered on Celite and concentrated. Theresidue was purified by column chromatography (silica gel, DCM/MeOH 0 to10%) to afford intermediate 7-2 (170 mg, 73%) as a white solid.

Step 2:(2R,3R,4R,5R)-5-(2-Amino-6-(cyclopropylamino)-9H-purin-9-yl)-2-(((tert-butyldiphenylsilyl)oxy)methyl)-4-fluoro-4-vinyltetrahydrofuran-3-ol(12). To a solution of intermediate 7-2 (168 mg, 0.48 mmol) in dry DMF(5 mL) was added imidazole (200 mg, 2.91 mmol) and TDPSCl (375 μL, 1.46mmol) at 0° C. The solution was stirred for 1 h at 0° C. The reactionmixture was then diluted with EtOAc (40 mL) and saturated NH₄Cl aqueoussolution (30 mL). The phases were separated and the organic layer waswashed with saturated NH₄Cl aqueous solution (4×20 mL), dried overNa₂SO₄ and concentrated. The residue was purified by columnchromatography (silica gel, DCM/MeOH 0 to 5%) to afford intermediate 7-3(254 mg, 89%) as a white solid.

Step 3:(2R,3R,4R,5R)-5-(2-Amino-6-(cyclopropylamino)-9H-purin-9-yl)-2-(((tert-butyldiphenylsilyl)oxy)methyl)-4-fluoro-4-(hydroxymethyl)tetrahydrofuran-3-ol(13). To a solution of intermediate 7-3 (250 mg, 0.42 mmol) in dioxane(6 mL) was added N-methylmorpholine-N-oxide (257 mg, 2.19 mmol) and OsO₄(4% in H₂O) (245 μL). The solution was stirred for 15 h at roomtemperature in the dark. Then, the mixture was diluted with EtOAc (30mL) and filtered on Celite. The solution was washed brine (20 mL), driedover Na₂SO₄ and concentrated. The residue was dissolved in DCM (6 mL)and added on NaIO₄ (adsorbed on silica) (2.7 g). The resulting slurrywas triturated for 15 h at RT. Then, the silica was filtered and washedthoroughly with DCM. The combined filtrates were concentrated. Theresidue was dissolved in EtOH (6 mL) and NaBH₄ (263 mg, 7.0 mmol) wasadded at 0° C. The solution was stirred for 3 h at 0° C. and thenquenched with saturated NH₄Cl aqueous solution (20 mL). The mixture wasextracted with EtOAc (2×25 mL). The combined organics were washed withbrine (10 mL), dried over Na₂SO₄ and concentrated. The residue waspurified by column chromatography (silica gel, DCM/MeOH 0 to 5%) toafford intermediate 7-4 (159 mg, 64%) as a white solid.

Step 4:9-((2R,3R,4R,5R)-5-(((tert-Butyldiphenylsilyl)oxy)methyl)-3-fluoro-4-((tetrahydro-2H-pyran-2-yl)oxy)-3-(((tetrahydro-2H-pyran-2-yl)oxy)methyl)tetrahydrofuran-2-yl)-N⁶-cyclopropyl-9H-purine-2,6-diamine(14). To a solution of intermediate 7-4 (150 mg, 0.25 mmol) in dry DCM(10 mL) was added 3,4-dihydro-2H-pyran (360 μL, 4.0 mmol) andcamphorsulfonic acid (100 mg, 0.43 mmol). The solution was stirred for 2h at room temperature and diluted with DCM (20 mL). Saturated NaHCO₃aqueous solution (20 mL) was added and the phases were separated. Theorganics were washed with brine (20 mL), dried over Na₂SO₄ andconcentrated. The residue was purified by column chromatography (silicagel, PE/EtOAc 0 to 40%) to afford intermediate 7-5 (146 mg, 76%) as awhite solid.

Step 5:((2R,3R,4R,5R)-5-(2-Amino-6-(cyclopropylamino)-9H-purin-9-yl)-4-fluoro-3-((tetrahydro-2H-pyran-2-yl)oxy)-4-(((tetrahydro-2H-pyran-2-yl)oxy)methyl)tetrahydrofuran-2-yl)methanol (15). To a solution of intermediate 7-5(140 mg, 0.18 mmol) in dry THE (5 mL) was added TBAF (1 M in THF) (360μL, 0.36 mmol). The solution was stirred for 1 h at room temperature andconcentrated. The residue was purified by column chromatography (silicagel, DCM/MeOH 0 to 5%) to afford intermediate 7-6 (86 mg, 90%) as awhite solid.

Step 6: (2S)-Isopropyl2-(((((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-(hydroxymethyl)tetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)amino) propanoate (16). To a solution of intermediate 7-6 (51 mg, 0.10mmol) in dry THF (3 mL) was added tert-butylmagnesium chloride (1 M inTHF) (130 μL, 0.13 mmol) drop-wise at 0° C. The solution was stirred for15 mins at 0° C. and for 45 mins at RT. Then, the reaction mixture wascooled down to 0° C. and a solution of isopropyl((R,S)-(pentafluorophenoxy)-phenoxy-phosphoryl)-L-alaninate (52 mg, 0.11mmol) in dry THE (1 mL) was added drop-wise. The resulting solution wasslowly warmed up to room temperature and stirred for 15 h. The reactionmixture was then diluted with EtOAc (10 mL) and saturated NH₄Cl aqueoussolution (8 mL). The phases were separated and the aqueous layer wasback-extracted with EtOAc (2×5 mL). The combined organics were washedwith saturated NH₄Cl aqueous solution (10 mL) and brine (10 mL), driedover Na₂SO₄ and concentrated. The residue was dissolved in HCl (1.25 Min i-PrOH) (2 mL). The solution was stirred for 2 h at room temperatureand concentrated. The residue was purified by column chromatography(silica gel, DCM/MeOH 0 to 10%) and by reverse phase columnchromatography (C-18 silica, H₂O/MeOH 0 to 100%). Compound 10 (25 mg,41%) was obtained as a white solid. ¹H NMR (400 MHz, CD₃OD) δ 7.81 (s,1H), 7.33-7.14 (m, 5H), 6.19 (d, J=18.3 Hz, 1H), 4.93-4.81 (m, 2H,overlapped with H₂O), 4.53-4.50 (m, 2H), 4.24-4.20 (m, 1H), 3.92-3.80(m, 2H), 3.55-3.44 (m, 1H), 2.91-2.88 (br. m, 1H), 1.27 (d, J=7.2 Hz,3H), 1.15 (t, J=7.0 Hz, 6H), 0.86-0.81 (m, 2H), 0.61-0.57 (m, 2H). ³¹PNMR (162 MHz, CD₃OD) δ 3.85 (s). MS (ESI) m/z calcd. for C₂₆H₃₆FN₇O₈P[M+H]⁺ 624.2. found 624.3.

Synthesis 8. Isopropyl((R)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-4-(trifluoromethyl)tetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate(Compound 11B)

Step 1: To a 3-neck round bottom flask was charged with anhydroustetrahydrofuran (100 mL) and LDA (25 mL, 50 mmol). The mixture wasstirred and cooled to −75° C. To this mixture was then slowly addedintermediate 8-1 (8.7 g, 50 mmol) while maintaining the batchtemperature below −74° C. The mixture was stirred at −76° C. for 60minutes and a solution of freshly distilled D-glyceraldehyde (6.5 g, 50mmol) in anhydrous THE (20 mL) was slowly added while maintaining batchtemperature below −74° C. After the addition, the mixture was stirredfor approximately 60 minutes and 100 g of 20% NH₄Cl solution was added.The mixture was slowly warmed to ambient temperature and transferred toa separatory funnel. The aqueous phase was separated and extracted withdichloromethane. The organic phases were combined, dried over MgSO₄,filtered, and concentrated to afford crude intermediate 8-2 and theresidue was purified by column chromatography to afford the product as ayellow oil (7.3 g, 50% yield). ¹H NMR (CDCl₃, 400 MHz): δ (ppm)1.33-1.43 (m, 9H), 4.06-4.42 (m, 6H); ¹⁹F NMR (CDCl₃, 376.5 MHz) δ (ppm)−73.83 (s, 1F), −73.00 (t, 3F).

Step 2: A mixture of intermediate 8-2 (3.0 g, 10 mmol), 20 g EtOH, and 2g of 12% sulfuric acid was refluxed at 78° C. for 5 hours. The mixturewas cooled to ambient temperature and 1 g of triethylamine was added toneutralize the acid. The mixture was concentrated to dryness. Theresidue was mixed with 20 g of toluene and the mixture was againconcentrated to dryness. The residue was dissolved in 15 g ofacetonitrile. To the solution was added a catalytic amount of4-dimethylaminopyridine (DMAP) and 4-chlorobenzoylchloride (5 g, 36mmol) at room temperature. The mixture was cooled in an ice water bathand then triethylamine (7.3 g, 72 mmol) was added. The mixture wasstirred at room temperature overnight. The reaction was quenched byadding water (60 mL) and the resulting solution was concentrated underreduced pressure. The residue was diluted with ethyl acetate (100 mL),washed with water, and brine (each 2×50 mL). The organic layer wasconcentrated under reduced pressure and the residue was purified bycolumn chromatography to afford intermediate 8-3 as a pale yellow solid(2.5 g, 50% yield). ¹H NMR (CDCl₃, 400 MHz) δ (ppm) 4.60-4.68 (m, 1H),4.75-4.84 (m, 1H), 4.92-5.00 (m, 1H), 6.06-6.16 (m, 1H), 7.40-7.53 (m,4H), 7.91-7.98 (m, 4H); ¹⁹F NMR (CDCl₃, 376.5 MHz) δ (ppm) −78.63 (s,1F), −74.74 (t, 3F).

Step 3: A dried round bottom flask was charged with intermediate 8-3 (5g, 10 mmol) and the solid was dissolved in anhydrous THE (50 mL). Thesolution was cooled to −20° C. Lithium tri-tert-butoxyaluminumy solution(1.0 M in THF) (17 mL, 17 mmol) was then added via addition funnel for20 minutes and the resulting mixture was stirred for 1 hour at −20° C.Ethyl acetate (12 mL) was added and the mixture was allowed to warmslowly to 0° C. A saturated aqueous solution of ammonium chloride (4.5mL) was then added and the mixture was concentrated in vacuo and dilutedwith EtOAc (100 mL). Aqueous HCl (3N, 30 mL) was added to dissolve thesolids. After the phase separation, the organic layer was washed withbrine (100 mL), dried over sodium sulfate, and concentrated underreduced pressure to give a solid. The residue solid was purified bycolumn chromatography to afford intermediate 8-4 as a white solid (3.5g, 70% yield). ¹H NMR (CDCl₃, 400 MHz) δ (ppm) 4.65-4.74 (m, 3H),5.57-6.17 (m, 2H), 7.31-7.47 (m, 4H), 7.91-8.01 (m, 4H); ¹⁹F NMR (CDCl₃,376.5 MHz) δ (ppm) −79.25 (d, 1F), −75.14 (d, 1F), −74.88 (d, 1F),−72.20 (d, 1F).

Step 4: Under nitrogen, intermediate 8-4 (1.5 g, 3 mmol) was dissolvedin dichloromethane (18 ml) at −20° C. and PPh₃ (1.5 g, 4.5 mmol) wasadded. The reaction mixture was stirred for 15 minutes and CBr₄ (2.4 g,4.5 mmol) was added portion-wise. The reaction was stirred for 1.5 hoursbetween −20° C. and −15° C. The reaction mixture was purified (withoutwork-up and concentration) by chromatography on a silica gel column toafford intermediate 8-5 (1.18 g, 70% yield). ¹H NMR (CDCl₃, 400 MHz) δ(ppm) 4.58-4.85 (m, 3H), 5.75-5.78 (m, 0.5H),6.41-6.70 (m, 1.4 H),7.38-7.47 (m, 4H), 7.94-8.04 (m, 4H); ¹⁹F NMR (CDCl₃, 376.5 MHz) δ (ppm)−79.27 (d, 1F), −75.23 (d, 1F), −72.81 (d, 1F), −70.46 (d, 1F).

Step 5: A three-neck round-bottomed flask was charged with6-chloro-2-aminopurine (1.1 g, 6.5 mmol) followed by anhydrous tBuOH (45mL) with stirring. To the above stirred solution was added potassiumtert-butoxide (1.5 g, 7 mmol) portion-wise at room temperature. After 30min, a solution of intermediate 8-5 (1.1 g, 2 mol) in anhydrousacetonitrile (4 mL) was added at room temperature. The mixture wasslowly heated to 50° C. and stirred for 22 h. Saturated aqueous solutionof ammonium chloride (4.5 mL) was added and the solution was dilutedwith ethyl acetate (60 mL), and washed with water and brine (each 2×30mL). The organic layer was concentrated under reduced pressure and theresidue was purified by column chromatography to afford the intermediate8-6 (0.5 g, 40% yield).

Step 6: A 5 mL flask was charged with methanamine (3 mL, 30% inmethanol) and stirred at 10±5° C. Intermediate 6 (325 mg, 0.5 mmol) wasadded in batches at 20±5° C. and the reaction was stirred for 1 hour toobtain a clear solution. The reaction was stirred for an additional 6-8hours, at which point TLC indicated that the intermediate was less than1% of the solution. The reactor was charged with solid NaOH (0.2 g),stirred for 30 minutes and concentrated. The resulting residue waspurified by column chromatography (DCM:MeOH=50:1 to 20:1) to affordintermediate 7 (120 mg, 65% yield).

Step 7: A solution of intermediate 8-7 (110 mg, 0.3 mmol) and(S)-2-[((S)-(2,3,4,5,6-pentafluorophenoxy)(phenoxy)phosphoryl)-amino]propionic acid isopropyl ester (150 mg, 0.33 mmol)were suspended in THE (2 mL) and stirred under nitrogen. The suspensionwas then cooled to a temperature below −15° C. and a 1.7 M solution oft-BuMgCl solution (0.5 mL, 0.85 mol) was slowly added while atemperature of −15 to −10° C. was maintained. The reaction was stirredfor an additional 16 hours, at which point TLC indicated that theintermediate was less than 5% of the solution. A saturated aqueoussolution of ammonium chloride (4.5 mL) was added to the suspension atroom temperature, and the solution was diluted with ethyl acetate (60mL), and washed with water and brine (each 2×30 mL). The organic layerwas concentrated under reduced pressure and the residue was purified bycolumn chromatography (DCM:MeOH=150:1 to 50:1) to afford the Compound11B (100 mg, 53% yield). ¹H NMR (CDCl₃, 400 MHz) δ (ppm) 1.71-1.18 (m,6H), 1.29-1.32 (m, 3H), 3.05 (s, 3H), 3.87-3.91 (m, 1H), 4.11-4.12 (bs,1H), 4.37-4.40 (m, 2H), 4.70-4.77 (m, 1H), 4.87-4.95 (m, 1H), 6.45-6.49(d, 1H), 7.20-7.38 (m, 5H), 7.73 (d, 1H); ¹⁹F NMR (CDCl₃, 376.5 MHz) δ(ppm) −178.22 (s, 1F), −76.37 (d, 3F).

Synthesis 9. Isopropyl((S)-(((2R,3R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4,4-difluoro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate

Isopropyl((S)-(((2R,3R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4,4-difluoro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninatecan be synthesized as described in in Hertel et al. J. Org. Chem. 1988,53, 2406 and Example 1. A non-limiting example is described below:

Using Reformatskii conditions, ethyl 2-bromo-2,2-difluoroacetate iscoupled to (R)-2,2-dimethyl-1,3-dioxolane-4-carbaldehyde I the presenceof activated Zinc to afford ethyl(3R)-3-(2,2-dimethyl-1,3-dioxolan-4-yl)-2,2-difluoro-3-hydroxypropanoate,which is then subjected to hydrolytic removal of the isopropylidinegroup and lactone closure as described in Hertel et al. Followingprotection with a CBz group,(2R,3R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4,4-difluoro-2-(hydroxymethyl)tetrahydrofuran-3-olcan be synthesized using the same procedures as described in Example 1,Part A, Steps 3-6.

(2R,3R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4,4-difluoro-2-(hydroxymethyl)tetrahydrofuran-3-olis then coupled to the dihydroquinine salt of isopropyl(hydroxy(phenoxy)phosphoryl)-L-alaninate (1-12) as described in Example1, Part C to afford isopropyl((S)-(((2R,3R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4,4-difluoro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate:

Synthesis 10. Isopropyl((S)-(((2R,3R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4,4-dichloro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate

Isopropyl((S)-(((2R,3R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4,4-dichloro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninatecan be synthesized as described in Pinho et al. J. Org. Chem. 2017, 27,3468 and Example 1. A non-limiting example is described below:

Isopropyl 2,2,2-trichloroacetate is coupled to(R)-2,2-dimethyl-1,3-dioxolane-4-carbaldehyde in the presence of TurboGrignard to afford ethyl(3R)-3-(2,2-dimethyl-1,3-dioxolan-4-yl)-2,2-dichloro-3-hydroxypropanoate,which is then subjected to acetic conditions and lactone closure asdescribed in Pinho et al. Following protection with a CBz group,(2R,3R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4,4-difluoro-2-(hydroxymethyl)tetrahydrofuran-3-olcan be synthesized using the same procedures as described in Example 1,Part A, Steps 3-6.

(2R,3R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4,4-dichloro-2-(hydroxymethyl)tetrahydrofuran-3-olis then coupled to the dihydroquinine salt of isopropyl(hydroxy(phenoxy)phosphoryl)-L-alaninate (1-12) as described in Example1, Part C to afford isopropyl((S)-(((2R,3R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4,4-dichloro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate:

Synthesis 11. Isopropyl((S)-(((2R,3R,4S,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-chloro-4-fluoro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate

(2R,3R,4R,5R)-5-(2-Amino-6-(methylamino)-9H-purin-9-yl)-4-chloro-4-fluoro-2-(hydroxymethyl)tetrahydrofuran-3-olcan be synthesized as described in US 20150175648 and the Example 1. Anon-limiting example is described below:

(3S,4R)-3-hydroxy-4-(hydroxymethyl)cyclopentan-1-one is firstCBz-protected to afford benzyl(((1R,2S)-2-(((benzyloxy)carbonyl)oxy)-4-oxocyclopentyl)methyl)carbonate and then subjected to NFSI (N-fluorobenzenesulfonimide) toafford benzyl(((1R,2R,3S)-2-(((benzyloxy)carbonyl)oxy)-3-fluoro-4-oxocyclopentyl)methyl)carbonate, an intermediate that is then subjected to NCS(N-chlorosuccinimide) to afford benzyl(((1R,2R,3S)-2-(((benzyloxy)carbonyl)oxy)-3-fluoro-4-oxocyclopentyl)methyl)carbonate as described in U.S. Patent '648.

(2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-chloro-4-fluoro-2-(hydroxymethyl)tetrahydrofuran-3-olis then coupled to the dihydroquinine salt of isopropyl(hydroxy(phenoxy)phosphoryl)-L-alaninate (1-12) as described in Example1, Part C to afford isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-chloro-4-fluoro-3-hydroxytetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate:

In one embodiment, the fluorination reaction affords a mixture of“α-fluoro” and “β-fluoro” lactone derivatives and the compounds areseparated by conventional methods known to a skilled artisan, forexample, column chromatography or crystallization, to isolate the twodiastereomers. In this embodiment, both diastereomers are carriedforward to afford the “α-fluoro” and “β-fluoro” final products:

In an alternative embodiment, the fluorination reaction is conductedwith N-fluoro-o-benzenedisulfonimide (NFOBS) or Selectfluor.

Example 3. Activity of Compound 1A Against Coronavirus in Huh7 Cells

The activity of Compound 1A was tested against the human coronavirusesalpha-229E and beta-OC43 in Huh7 cells.

Huh7 cells were seeded in 96-well plates at a concentration that yielded80-100% confluent monolayers in each well after overnight incubation.Compound 1A was dissolved in DMSO to 10 mg/mL and 8 half-log serialdilutions in test medium (modified Eagle's medium containing 5% fetalbovine serum and 50 μL gentamicin) were prepared with the highestconcentration of 50 μg/mL. 100 μL of each concentration were added to 5test wells on the 96-well plate and 3 wells were infected with testvirus in test medium (≤100 CCID₅₀ per well). An equivalent amount oftest medium was added to the remaining test wells to assess toxicity touninfected cells. Six wells were infected to serve as untreated viruscontrols. Media only was added to 6 wells to serve as cell controls.Plates were incubated at 37° C. in a humidified 5% CO₂ atmosphere untilcytopathic effect (CPE) was observed microscopically.

To obtain the CPE endpoint, wells were stained with 0.011% neutral reddye for approximately 2 hours. The dye was siphoned off and wells wererinsed once with phosphate-buffered saline to remove residual,unincorporated dye. 200 μL of 50:50 Sorensen citrate buffer/ethanol wasadded for >30 min with agitation and then light absorbance at 540 nm wasmeasured on a spectrophotometer.

To obtain the virus yield reduction (VYR) endpoint, supernatant fluidfrom 3 replicate wells of each compound concentration were pooled andvirus titer was measured using a standard endpoint dilution CCID₅₀ assayand titer calculations using the Reed Muench (1948) equation (Reed, Uand Muench, H. Am. J. Hygiene 27:493-497 (1948)). The concentration ofcompound required to reduce virus yield by 1 log₁₀ (EC₉₀) was determinedusing regression analysis.

As shown in Table 1, Compound 1A is potent against both the alpha-229Ecoronavirus and the beta-OC43 coronavirus. Compound 1A exhibits an EC₉₀value of 0.71 μM against alpha-229E in the virus yield reduction assayand an EC₉₀ value of 0.29 μM against beta-OC43. Additionally, Compound1A exhibits high CC₅₀ values and selectivity indexes (SI) against boththe alpha and beta coronaviruses. For example, against the betacoronavirus, Compound 1A has a selectivity index of greater than 170when measured using the viral yield reduction assay and a CC₅₀ value ofgreater than 50 μM when measured in neutral red assay.

TABLE 1 Activity of Compound 1A against Coronaviruses Alpha-229E andBeta-OC43 Visual Neutral Red VYR Virus in Huh7 EC₅₀ CC₅₀ EC₅₀ CC₅₀ EC₉₀cells (μM) (μM) SI (μM) (μM) SI (μM) SI Alpha-229E 1 >50 >50 1 >50 >500.71 >70 Beta-OC43 NT >50 NT NT >50 NT 0.29 >170 Visual and neutral redSI: CC₅₀/EC₅₀ VYR S1: CC₅₀/_(EC90) NT: not tested

Example 4. Activity of Compound 1A and 1B Against Coronavirus in BHK-21and MES-21 Cells

Compound 1A and Compound 1B were tested for activity against humancoronavirus in BHK-21 cells (Table 2A and Table 2B) and MES-1 cells(Table 3A and Table 3B). The EC₅₀ and the CC₅₀ was determined andcompared to Sofosbuvir.

Compound activity against coronavirus was based on inhibition of virusinduced cytopathogenicity acutely infected with a multiplicity ofinfection (m.o.i.) of 0.01. After a 3-day incubation at 37° C. cellviability was determined by the MTT method as described by Pauwels etal. (J. Virol. Methods 1988, 20, 309-321).

To determine the cytotoxicity, cells were seeded at an initial densityof 1×106 cells/mL in 96 well plates containing Minimum Essential Mediumwith Earles's salts (MEM-E), L-glutamine, 1 mM sodium pyruvate and 25mg/L kanamycin, supplemented with 10% fetal bovine serum. Cell cultureswere then incubated at 37° C. in a humidified 5% CO₂ atmosphere in theabsence or presence of serial dilutions of test compounds. Cellviability was determined by the MTT method.

TABLE 2A Activity of Select Compounds against HCoV in BHK-21 CellsCompound CC₅₀ [uM]^(a) EC₅₀ [uM]^(b)

  Compound 1A >100 1.6

  Compound 1B >100 2.5

  Sofosbuvir >100 >100 ^(a)Compd conc. (μM) required to reduce theviability of mock infected BHK cells by 50% as determined by the MTTmethod after 3 days of incubation ^(b)Compd conc. (μM) required toachieve 50% protection of BHK cells from virus-induced cytopathogenicityas determined by the MTT method at day 3 post-infection

TABLE 2B Activity of Select Compounds against HCoV in BHK-21 CellsCompound CC₅₀ [uM]^(a) EC₅₀ [uM]^(b)

  Compound 1A >100 2.0

  Compound 1B >100 2.9

  Sofosbuvir >100 >100 ^(a)Compd conc. (μM) required to reduce theviability of mock infected BHK cells by 50% as determined by the MTTmethod after 3 days of incubation ^(b)Compd conc. (μM) required toachieve 50% protection of BHK cells from virus-induced cytopathogenicityas determined by the MTT method at day 3 post-infection

TABLE 3A Activity of Select Compounds against HCoV in MES-1 Cells CC₅₀[uM]^(c) EC₅₀ [uM]^(d)

  Compound 1A >100 1.6

  Compound 1B >100 2.0

  Sofosbuvir >100 >100 ^(c)Compd conc. (μM) required to reduce viabilityof mock infected MES-1 cells by 50% as determined by the MTT methodafter 3 days of incubation ^(d)Compd conc. (μM) required to achieve 50%protection of MES-1 cells from virus-induced cytopathogenicity asdetermined by the MTT method at day 3 post-infection

TABLE 3B Activity of Select Compounds against HCoV in MES-1 Cells CC₅₀[uM]^(c) EC₅₀ [uM]^(d)

  Compound 1A >100 2.0

  Compound 1B >100 2.2

  Sofosbuvir >100 >100 ^(c)Compd conc. (μM) required to reduce viabilityof mock infected MES-1 cells by 50%, as determined by the MTT methodafter 3 days of incubation. ^(d)Compd conc. (μM) required to achieve 50%protection of MES-1 cells from virus-induced cytopathogenicity asdetermined by the MTT method at day 3 post-infection

Example 5. Activity of Compound 1A Against SARS-CoV and SARS-CoV-2

Compound 1A was tested against SARS-CoV in Huh7 cells and SARS-CoV-2 indifferentiated normal human bronchial epithelial (dNHIBE, also referredto as HAL (human airway epithelial)) cells and the results are providedin Table 4. The CC₅₀ was determined using the neutral red assay and theEC₉₀ and SI were determined using the virus yield reduction assay. TheEC₉₀ is provided in μg/mL and μM. Compound 1A exhibits an EC₉₀ of 0.34μM against SARS-CoV and an EC₉₀ of 0.64 μM against SARS-CoV-2.

TABLE 4 Activity of Compound 1A Against SARS-CoV and SARS-CoV-2 NeutralRed HuCoV Assay Virus Yield Reduction Assay Virus Cell CC₅₀ EC₉₀ EC₉₀Selectivity (strain) Line (μg/mL) (μg/mL) (μM) Index SARS- Huh7 >50  0.20.34 >250 CoV (Urbani) SARS- dNHBE >50¹ 0.37² 0.64 >135 CoV-2 (WA1)¹CC₅₀ was estimated by visual inspection of the cells ²Value representsthe mean of two replicate EC₉₀ determinations, 0.33 and 0.41 μg/mL

The activity of Compound 1A was evaluated in Huh-7 cells infected withSARS-CoV (Urbani) in a neutral red (NR) assay to assess cytotoxicity andthen tested using a virus yield reduction (VYR) assay to assessantiviral activity.

Neutral red assay: Compound 1A was dissolved in 100% DMSO at aconcentration of 10 mg/mL and serially diluted using eight half-logdilutions in test medium (Minimum Essential Medium supplemented with 5%FBS and 50 μg/mL gentamicin). The starting (high) test concentration was50 μg/mL. Each dilution was added to 5 wells of a 96-well plate with80-100% confluent Huh7 or RD cells (hCoV beta OC43 only). Three wells ofeach dilution were infected with virus and two wells remained uninfectedas toxicity controls. Six untreated wells were infected as viruscontrols and six untreated wells were left uninfected to use as cellcontrols. Viruses were diluted to a specific 50% cell culture infectiousdose (CCID₅₀) per mL to achieve the lowest possible multiplicity ofinfection (MOI) that would yield >80% toxicity within 5-7 days. The MOIwas 0.03 CCID₅₀/cell. Plates were incubated at 37±2° C., 5% CO2.

On day 7 post-infection (p.i.), the plates were stained with neutral reddye for approximately 2 hours (±15 minutes). Supernatant dye wasremoved, wells were rinsed with PBS, and the incorporated dye wasextracted in 50:50 Sorensen citrate buffer/ethanol for >30 minutes andthe optical density was read on a spectrophotometer at 540 nm. Opticaldensities were converted to percent of cell controls and theconcentration of Compound 1A required to cause 50% cell death in theabsence of virus was calculated (CC₅₀). The selective index (SI) is theCC₅₀ divided by the EC₅₀.

Virus yield reduction assay: Vero76 cells were seeded in 96-well platesand grown overnight (37° C.) to 80% confluency. A sample of thesupernatant fluid from each compound concentration was collected on day3 post-infection (3 wells pooled) and tested for virus titer using astandard endpoint dilution CCID₅₀ assay and titer calculations using theReed-Muench (1948) equation (Reed, L J and Muench, H. Am. J. Hygiene27:493-497 (1948)). The concentration of compound required to reducevirus yield by 1 log 10 (EC₉₀) was calculated by regression analysis.

The antiviral activity of Compound 1A was next evaluated againstSARS-CoV-2 (WA1) using differentiated normal human bronchial epithelial(dNHBE; HAE (human airway epithelial) cells made to order by MatTekCorporation (Ashland, MA).

Cell Culture: dNHBE cells were grown on 6 mm mesh disks and arrived inkits with either 12- or 24-well transwell inserts. During transportationthe tissues were stabilized on a sheet of agarose, which was removedupon receipt. One insert was estimated to consist of approximately1.2×106 cells. Kits of cell inserts (EpiAirway™ AIR-100, AIR-112)originated from a single donor, #9831, a 23-year old, healthy,non-smoking, Caucasian male. The cells have unique properties in forminglayers, the apical side of which is exposed only to air and that createsa mucin layer. Upon arrival, the cell transwell inserts were immediatelytransferred to individual wells of a 6-well plate according tomanufacturer's instructions, and 1 mL of MatTek's proprietary culturemedium (AIR-100-MM) was added to the basolateral side, whereas theapical side was exposed to a humidified 5% CO₂ environment. Cells werecultured at 37° C. for one day before the start of the experiment. Afterthe 24 hour equilibration period, the mucin layer, secreted from theapical side of the cells, was removed by washing with 400 μL pre-warmed30 mM HEPES buffered saline solution 3×. Culture medium was replenishedfollowing the wash steps.

Viruses: Virus was diluted in AIR-100-MM medium before infection,yielding a multiplicity of infection (MOI) of approximately 0.0015CCID₅₀ per cell.

Experimental design: Each compound treatment (120 μL) and virus (120 μL)was applied to the apical side. At the same time, the compound treatment(1 mL) was applied to the basal side for a 2-h incubation. As a viruscontrol, some of the cells were treated with placebo (cell culturemedium only). Following the 2-h infection, the apical medium wasremoved, and the basal side was replaced with fresh compound or medium(1 mL). The cells were maintained at the air-liquid interface. On day 5,cytotoxicity (CC₅₀ values) in the placebo-treated inserts was estimatedby visual inspection, and the medium was removed from all inserts anddiscarded from the basal side. Virus released into the apicalcompartment of the dNHBE cells was harvested by the addition of 400 μLof culture medium that was pre-warmed at 37° C. The contents wereincubated for 30 minutes, mixed well, collected, thoroughly vortexed andplated on Vero 76 cells for VYR titration. Duplicate wells were used forvirus control and cell controls.

Determination of virus titers from each treated cell culture: Vero 76cells were seeded in 96-well plates and grown overnight (37° C.) toconfluence. Samples containing virus were diluted in 10-fold incrementsin infection medium and 200 μL of each dilution transferred intorespective wells of a 96-well microtiter plate. Four microwells wereused for each dilution to determine 50% viral endpoints. After 5 days ofincubation, each well was scored positive for virus if any cytopathiceffect (CPE) was observed as compared with the uninfected control andcounts were confirmed for endpoint on days 6 and 7. The virus dose thatwas able to infect 50% of the cell cultures (CCID₅₀ per 0.1 mL) wascalculated by the Reed-Muench method (1948) (Reed, L J and Muench, H.Am. J. Hygiene 27:493-497 (1948)) and the 90% effective concentration(EC₉₀; concentration to reduce virus yield by 1 log 10) was determinedby regression analysis. The day 5 values were reported. Untreated,uninfected cells were used as the cell controls.

Example 6. In Vitro Activity of Compound 1A and Other Oral AntiviralDrugs Against Various Human Coronaviruses

Compound 1A and other oral antiviral drugs were tested against varioushuman coronaviruses (Table 5) in various cell lines. The datademonstrate the potent in vitro activity of Compound 1A against severalCoVs, with individual EC₉₀ values ranging from 0.34 to 1.2 μM againstHCoV-229E, HCoV-OC43, SARS-CoV-1 and SARS-CoV-2 and less activityagainst MERS-CoV (average EC₉₀=36 μM).

TABLE 5 Activity of Compound 1A and Other Oral Antiviral Drugs AgainstHuman Coronaviruses Virus Yield Neutral Red Assay Reduction SelectivityVirus EC₅₀ CC₅₀ Assay Index (genus) Cell line Compound (μM) (μM) EC₉₀(μM) (CC₅₀/EC₉₀) HCoV-229E BHK-21 Compound 1A  1.8^(a,b) >100   >58^(c)(alpha) sofosbuvir >100^(b)   >100  N/A  Huh-7 Compound 1A 1.7/1.6 >861.0  >75 chloroquine 8.1  21 <0.050    2.6^(c) hydroxychloroquine 7.4 26 <0.048    3.5^(c) HCoV-OC43 Huh-7 Compound 1A ND^(d) >86 0.5/<0.03 >170/>3100 (beta) RD Compound 1A 2.8 >86 2.2  >39 MERS-CoVHuh-7 Compound 1A 15/36 >86 17/56  >5/>1.5 (beta) SARS-CoV-1 Huh-7Compound 1A ND >86 0.34 >250  (beta) SARS-CoV-2 HAE Compound 1A ND>86^(e)/>8.6^(e)  0.64^(f)/0.47^(g)  >130/>18  (beta) N⁴-hydroxycytidine >19^(e)  3.9^(h)   >5.1 ^(a)Average of 2 experiments (1.6 and 2.0 μM)^(b)EC₅₀ determined by dye staining (virus yield reduction substantiallyoverestimates antiviral potency of cytotoxic compounds) ^(c)CC₅₀/EC₅₀^(d)Not determined (no cytopathic effect with this virus in this cellline) ^(e)Cytotoxicity assessed by visual inspection of cell monolayers^(f)Average of two replicates (0.57 and 0.70 μM) ^(g)Average of tworeplicates (0.52 and 0.42 μM) ^(h)Average of two replicates (4.7 and 3.1μM) BHK-21, baby hamster kidney cell line Huh-7, human hepatocytecarcinoma cell line (established ability to form triphosphate fromCompound 1A) RD, human rhabdomyosarcoma cell line (unknown ability toform triphosphate from Compound 1A) HAE, human airway epithelial cellculture (established ability to form triphosphate from Compound 1A)(established ability to form triphosphate from Compound 1A)

In an initial screening, BHK-21 cells acutely infected with a seasonalhuman alpha coronavirus, HCoV-229E, were exposed to serial dilutions ofCompound 1A. After a 3-day incubation, the effective concentration ofCompound 1A required to achieve 50% inhibition (EC₅₀) of thevirus-induced cytopathic effect (CPE) from two independent experimentsaveraged 1.8 μM. In contrast, the 2′-fluoro-2′-methyl uridine nucleotideprodrug sofosbuvir did not inhibit HCoV-229E replication atconcentrations as high as 100 μM (Table 5). No toxicity was detectedfrom either drug.

The in vitro potency of Compound 1A against HCoV-229E, HCoV-OC43(another seasonal human coronavirus strain), MERS-CoV and SARS-CoV-1 wasthen evaluated in Huh-7 cell-based assays. This human hepatocarcinomacell line was selected based on its ability to activate Compound 1Aintracellularly to its triphosphate metabolite, unlike MRC-5 cells inwhich Compound 1A lacked activity against HCoV-229E (EC₅₀>100 μM) asreported in Good, S. S. et al. PLoS One 15(1), e0227104 (2020)).Antiviral activity was assessed by two different methods after exposureof Huh-7 cells to virus and serial dilutions of test compound bydetermining 1) the EC₅₀ for virus-induced CPE by neutral red dyestaining after a 5-day (229E and OC43) or 7-day (MERS and SARS)incubation and 2) the effective concentration required to reducesecretion of infectious virus into the culture medium by 90% (EC₉₀)after a 3-day incubation using a standard endpoint dilution CCID₅₀ assayto determine virus yield reduction (VYR). Half-maximal cytotoxicity(CC₅₀) was measured by neutral red staining of compound-treatedduplicates in the absence of virus. Although a robust VYR endpoint wasobtained in Huh-7 cells infected with HCoV-OC43 or SARS-CoV-1, CPE wasnot observed and EC₅₀ values using neutral red staining were notobtained with these viruses. Individual determinations of EC₉₀ valuesfor Compound 1A against HCoV-229E, HCoV-OC43 and SARS-CoV-1 ranged from0.34 to 1.2 μM, whereas the value against MERS-CoV averaged 37 μM (Table5). No cytotoxicity was detected with Compound 1A up to 86 μM, thehighest concentration tested.

Chloroquine and hydroxychloroquine appeared to be quite potent againstHCoV-229E and HCoV-OC43 based on their EC₉₀ values of <0.05 μM obtainedusing VYR measurements (Table 5). The respective EC₅₀ values for thesetwo drugs (8.1 and 7.4 μM), obtained using the neutral red assay, weresubstantially higher and only 2.6- to 3.6-fold less than thecorresponding CC₅₀ values, indicating considerably lower potencies andpoor selectivity indices. These differences illustrate an inherent errorin assessing antiviral activities of cytotoxic compounds using onlymeasurements of VYR. When cells are poisoned by toxic drugs and areprogressing toward death, their ability to support viral replication andpropagation in addition to their own health likely is greatlydiminished. At the point when cell death is detected by staining, viralyield reduction measurements likely reflect a combination of antiviralactivity and cytotoxicity, thus overestimating antiviral potencies.

In contrast to data published in Wang, M. et al. (Cell Research 2020,30, 269), Huh-7 cells were not permissive for replication of SARS-CoV-2.An assay was developed using human airway epithelial (HAE) cellpreparations, a highly relevant in vitro model of the lung, which hasbeen established as a more representative system than cell lines forSARS-CoV-2 replication (Jomsdottir, H. R., Virol. J. 13, 24 (2016)).These primary cells form polarized monolayers, the apical side of whichis exposed to air and produces a mucin layer, consistent with thephysiology of the human airways (Jomsdottir, H. R., Virol. J. 13, 24(2016)). Average EC₉₀ and CC₅₀ values for Compound 1A against SARS-CoV-2from two separate HAE assays (0.5 and >86 μM, respectively) were in thesame range as those obtained for HCoV-OC43 and SARS-CoV-1 (Table 5).

In the second HAE assay, the activity of Compound 1A was tested inparallel with N⁴-hydroxycytidine with recently reported in vitro and invivo activity against SARS-CoV-2 (Sheahan, T. P. et al. Sci. Transl.Med. 12, eabb5883 (2020)). The potency of N⁴-hydroxycytidine againstSARS-CoV-2 (EC₉₀=3.9 μM) was 8 times less than that of Compound 1A inthe same experiment.

A 30-fold difference of Compound 1A activity between MERS-CoV and otherCoVs was observed. Nucleotide and nucleotide analogue selection isachieved at the CoV RdRp active site, the nsp12 gene product activatedby its processivity co-factors nsp7 and nsp8 (Subissi, L., Proc. Natl.Acad. Sci. USA 111 (37) 3900-9 (2014)). Conserved amino acid motifs Aand C are involved in phosphodiester bond formation, whereas motifs Fand B participate in nucleotide channeling and binding at the activesite, respectively. No significant structural differences are apparentbetween MERS-CoV and other CoVs in these essential motifs. With asimilar ribose modification between Compound 1A and sofosbuvir, it isunlikely that the selective lack of activity of sofosbuvir would be dueto excision by the CoV exonuclease carried by nsp14 (Ferron, F., Proc.Natl. Acad. Sci. USA 115 (2) 162-171 (2018)).

Cells, Antivirals and Viruses

BHK-21 (baby hamster kidney) cells, Huh-7 (human hepatocarcinoma) cells,RD (human rhabdomyosarcoma) cells and the seasonal human coronaviruses(HCoV-229E and HCoV-OC43) were obtained from American Type CultureCollection, Manassas, VA MERS-CoV (EMC), SARS-CoV-1 (Urbani) andSARS-CoV-2 (USA-WA1/2020) were supplied by The Centers for DiseaseControl and Prevention, Atlanta, GA The HAE cell preparations(EpiAirway™ AIR-100 or AIR-112) were purchased from MatTek Corporation,Ashland, MA Compound 1A and N4-hydroxycytidine were prepared for AteaPharmaceuticals by Topharman Shanghai Co., Ltd., Shanghai, China andOxeltis, Montpellier, France, respectively. Chloroquine andhydroxychloroquine were purchased from Mason-Chem, Palo Alto, CA andsofosbuvir was purchased from Pharma Sys, Inc., Cary, NC

Antiviral Assays

BHK-21 cells: Test compounds were dissolved in DMSO at 100 mM and thendiluted in Minimum Essential Medium with Earle's salts (MEM-E)containing 1 mM sodium pyruvate and 25 μg/mL kanamycin, supplementedwith 10% FBS (growth medium) to final concentrations of 100, 20, 4 and0.8 μM (two 24-well replica plates each). After BHK-21 cells were grownto confluency in 96-well plates, growth medium was replaced with freshmaintenance medium (growth medium with 1% inactivated FBS in place of10% FBS) containing serially diluted test compound and HCoV-229E at amultiplicity of infection (MOI) of 0.01. Uninfected cells in thepresence of serially diluted compound were used to assess thecytotoxicity of compounds. After a 3-day incubation at 37° C. in ahumidified 5% CO₂ atmosphere, cell viability was determined by the MTTmethod (Pauwels, R et al. J. Virol. Methods 20(4):309-321 (1988)). Theeffective concentration of test compound required to preventvirus-induced cytopathic effect (CPE) by 50% (EC₅₀) and to cause 50%cell death in the absence of virus (CC₅₀) were calculated by regressionanalysis.

Huh-7 and RD cells: The antiviral activities of test compounds wereevaluated against human coronaviruses alpha (229E), beta (OC43), MERS(EMC) and SARS (Urbani) using a neutral red assay to determineinhibition of virus-induced and compound-induced CPE and using a virusyield reduction (VYR) assay as a second, independent determination ofthe inhibition of virus-induced CPE.

Neutral red assay: Test compounds were dissolved in DMSO at aconcentration of 10 mg/mL and serially diluted using eight half-logdilutions in test medium (Minimum Essential Medium supplemented with 5%FBS and 50 μg/mL gentamicin) so that the highest test concentration was50 μg/mL. Each dilution was added to 5 wells of a 96-well plate with80-100% confluent Huh-7 or RD cells (OC43 only). Three wells of eachdilution were infected with virus, and two wells remained uninfected astoxicity controls. Six untreated wells were infected as virus controlsand six untreated wells were left uninfected to use as virus controls.Viruses were diluted to achieve MOIs of 0.003, 0.002, 0.001 and 0.03CCID₅₀ per cell for 229E, OC43, MERS and SARS, respectively. Plates wereincubated at 37±2° C. in a humidified atmosphere containing 5% CO₂.

On day 5 (229E and OC43) or day 7 (MERS and SARS) post-infection, whenuntreated virus control wells reached maximum CPE, the plates werestained with neutral red dye for approximately 2 hours (±15 minutes).Supernatant dye was removed, wells were rinsed with PBS, and theincorporated dye was extracted in 50:50 Sorensen citrate buffer/ethanolfor >30 minutes and the optical density was read on a spectrophotometerat 540 nm. Optical densities were converted to percent of controls andthe concentrations of test compound required to prevent virus-inducedCPE by 50% (EC₅₀) and to cause 50% cell death in the absence of virus(CC₅₀) were calculated.

Virus yield reduction assay: Vero 76 cells were seeded in 96-well platesand grown overnight (37° C.) to confluence. A sample of the supernatantfluid from each compound concentration was collected on day 3 postinfection (3 wells pooled) and tested for virus titer using a standardendpoint dilution CCID₅₀ assay and titer calculations using theReed-Muench equation (1948) (Reed, U and Muench, H. Am. J. Hygiene27:493-497 (1948)) and the concentration of compound required to reducevirus yield by 90% (EC₉₀) was determined by regression analysis.

HAE Cell Preparations

The antiviral activities of test compounds were evaluated againstSARS-CoV-2 (USA-WA1/2020) using made to order human airway epithelial(HAE) cells.

Cell Culture: HAE cells were grown on 6 mm mesh disks and arrived inkits with either 12- or 24-well transwell inserts. During transportationthe tissues were stabilized on a sheet of agarose, which was removedupon receipt. One insert was estimated to consist of approximately1.2×10⁶ cells. Kits of cell inserts (EpiAirway™ AIR-100 or AIR-112)originated from a single donor, #9831, a 23-year old, healthy,non-smoking, Caucasian male. The cells form polarized monolayers, theapical side of which is exposed to air and creates a mucin layer. Uponarrival, the cell transwell inserts were immediately transferred toindividual wells of a 6-well plate according to the manufacturer'sinstructions, and 1 mL of MatTek's proprietary culture medium(AIR-100-MM) was added to the basolateral side, whereas the apical sidewas exposed to a humidified 5% CO₂ environment. Cells were cultured at37° C. in a humidified atmosphere containing 5% CO₂ for one day beforethe start of the experiment. After the 24-h equilibration period, themucin layer, secreted from the apical side of the cells, was removed bywashing with 400 μL pre-warmed 30 mM HEPES buffered saline solution 3×.Culture medium was replenished following the wash steps.

Viruses: Virus was diluted in AIR-100-MM medium before infection toyield a MOI when added to cultures of approximately 0.0015 CCID₅₀ percell.

Experimental design: Each compound treatment (120 μL) and virus (120 μL)was applied to the apical side, and the compound treatment (1 mL) wasapplied to the basal side. As a virus control, some of the cells weretreated with cell culture medium only. After a 2-h infection incubation,the apical medium was removed, and the basal medium was replaced withfresh compound or medium (1 mL). The cells were maintained at theair-liquid interface. On day 5, cytotoxicity (CC₅₀ values) in theuninfected, compound-treated inserts was estimated by visual inspection,and the basal medium was removed from all inserts and discarded. Virusreleased into the apical compartment of the HAE cells was harvested bythe addition of 400 μL of culture medium that was pre-warmed at 37° C.The contents were incubated for 30 min, mixed well, collected,thoroughly vortexed and plated on Vero 76 cells for VYR titration.Separate wells were used for virus control and duplicate wells were usedfor untreated cell controls. Virus titers from each treated culture weredetermined as described above.

Example 7. Compound 1A Triphosphate Levels in Human Nasal and BronchialCells

Compound 1A (10 μM) was incubated in triplicate with human nasal andbronchial epithelial cells for 8 hours. At the end of the 8-hr exposureto individual test articles, the incubation medium was removed and thecell layer was washed with Hepes buffered saline solution (HBSS). HBSSwas removed, followed by the addition of fresh cell culture mediumwithout test article. At 0, 15, 24, 48, and 72 hours after the removalof test article, the extracellular medium was removed, and the celllayer was rinsed with HIBSS. The cells were scraped off from plates andsuspended in cold 6000 methanol in water containing the internalstandard AT 9005 and stored at ca. −20° C., followed by centrifugationfor LC/MS/MS analysis for the formation of the correspondingtriphosphate metabolite of Compound 1A, Compound 1-6 (Scheme 1). Table 6provides the mean intracellular concentration of the triphosphatemetabolite Compound 1-6 at each of the time points. FIG. 1 is a graph ofthe concentration of Compound 1-6 at each time point post-exposure inbronchial cells and nasal cells. The half-life (t_(1/2)) in nasal cellswas 38 hours and 39 hours in bronchial cells. The triphosphate level inbronchial cells was greater than in nasal cells, but substantial levelsof triphosphate were formed in both. The half-life in both cells wasover 1.5 days and no toxicity was observed up to 100 μM.

TABLE 6 Intracellular Concentration of Triphosphate Concentrations inBronchial and Nasal Cells Mean Intracellular Time After Compound 1-6Cell Type Washout (h) Concentration (μM)¹ Human 0 698 bronchial 15 560epithelial cells 24 462 48 290 72 217 Human nasal 0 236 epithelial cells15 204 24 170 48 107 72 73.8 ¹Calculated using an average volume of 1320microns³ for alveolar type I and II epithelial cells (Crapo, J. D. etal. 1982 Am. Rev. Respir. Dis. 126(2): 332-7. doi:10.1164/arrd.1982.126.2.332.)

FIG. 2 and FIG. 3 are bar graphs of the triphosphate levels in bronchialand nasal cells, respectively, at each of the time points. FIGS. 2 and 3compare the triphosphate level formed from Compound 1A to thetriphosphate level formed from ALS-8112 (shown below) and the 4′-Mesubstituted prodrug (isopropyl((S)-(((2R,3R,4R,5R)-5-(2-amino-6-(methylamino)-9H-purin-9-yl)-4-fluoro-3-hydroxy-2,4-dimethyltetrahydrofuran-2-yl)methoxy)(phenoxy)phosphoryl)-L-alaninate,shown below on the left). ALS-8112 is a clinically effective drugagainst RSV with an in vitro EC₉₀ of 1.3-2.7 μM in RSV-infected HAEcells (Deval, J. et al. 2015 PLoS Pathog 11(6): e1004995).

As shown in FIGS. 2 and 3 , substantially more triphosphate is formedfrom Compound 1A compared to ALS-8112 or the 4′-Me substituted prodrugin both human bronchial and nasal cells. At end of 8 hour incubationwith each drug at a concentration of 10 μM, ratios of triphosphate fromCompound 1A vs. ALS-8112 and the 4′-Me substituted prodrug were 2 and 84in bronchial cells and 1 and 14 in nasal cells, respectively. Ratios oftriphosphate from Compound 1A vs. ALS-8112 and the 4′-Me substitutedprodrug were 5 and 54 in bronchial cells and 3 and 8 in nasal cells,respectively, 15 hours after washout.

Example 8. Triphosphate Levels in Tissues of Non-Human Primates afterOral Administration of Compound 2A

Non-human primates were administered a three-day oral dosing regimen ofCompound 2A to achieve steady state levels. The primates were given one60 mg/kg dose followed by five 30 mg/kg doses every 12 hours (doses wereallometrically scaled from clinical dosing regimen of 100 mg loadingdose+550 mg twice a day (BID)).

The plasma PK of metabolites Compound 1A, Compound 1-2, and thetriphosphate surrogate Compound 1-7 were determined. Just prior to thepenultimate dose and at 0.5, 1, 2, 4, 6, 8 and 12 h (just prior to thelast dose) thereafter, blood samples were obtained from 3 monkeys andmixed with EDTA. Plasmas were then prepared by centrifugation andanalyzed for concentrations of Compound 1A, Compound 1-2, and Compound1-7 by LC-MS/MS. (Triphosphate Compound 1-6 is produced in the cell anddoes not leave. It is therefore not measurable in the plasma. However,the 5′-OH metabolite Compound 1-7 (see Scheme 1) is exported from thecell, and therefore is measurable in plasma and can act as a surrogatefor the intracellular active metabolite Compound 1-6.) The plasma PKdata for the metabolites are given in Table 7.

TABLE 7 Plasma PK data for Metabolites 1A, 1-2, and 1-7 followingCompound 2A Dosing Mean Plasma Pharmacokinetic Parameters C_(max)C_(12 h) T_(max) T_(1/2) AUC_(0-12 h) Compound (μM) (μM) (h) (h) (μM*h)1A (parent 0.64 Not 0.5-1 0.74 0.44 prodrug) detected 1-2 0.68 0.20  1-48.8 4.4 (intermediate prodrug) 1-7 (plasma 0.16 0.10 2 17 0.47 surrogatefor intracellular TP)

FIGS. 4, 5, and 6 are graphs of the mean plasma profile of Compound 1A,Compound 1-2, and Compound 1-7, respectively, in the non-human primatesfollowing administration of oral doses of Compound 2A (30 mg/kg BID for3 days). Plasma trough concentrations (mean of 0- and 12 h time points)for Compound 1-2 (intermediate prodrug) and Compound 1-7 (surrogate forintracellular TP levels) are 0.20 and 0.11 μM, respectively. Theprofiles show rapid conversion of Compound 1A to Compound 1-2 andCompound 1-7 (a surrogate for triphosphate Compound 1-6).

Lung, kidney, and liver tissue levels were determined for triphosphateCompound 1-6, Compound 1A, and other metabolites at 12, 24, and 48 hourspost last dose (3 males per time point) as shown in FIG. 7A and FIG. 7B.As described above, three male non-naïve cynomolgus monkeys wereadministered a 60 mg/kg loading dose followed by five 30 mg/kg dosesevery 12 h of Compound 2A. Samples of plasma, lung, kidney and livertissue were collected at 12, 24, and 48 hours post last dose from thethree anesthetized animals at each time point and immediatelyflash-frozen in liquid nitrogen. Approximately 0.5 g of each sample oftissue was homogenized using a Polytron in 5 volumes (5 mL/g) 70%methanol:30% 268 mM EDTA adjusted to pH 7.8 and containing appropriateinternal standards in tubes immersed in a dry ice:ethanol bath.Homogenates were analyzed for concentrations of Compound 1A, Compound1-2, Compound 1-6, and Compound 1-7 by LC-MS/MS.

The trough (12 h) levels of active metabolite triphosphate Compound 1-6in lung, kidney and liver non-human primate tissues was 0.14 μM, 0.13μM, and 0.09 μM, respectively. The triphosphate species concentrationwas 1.6-fold greater in the lung compared to the liver at 12-hoursteady-state trough levels. Table 8 provides the mean intracellularconcentration of the triphosphate metabolite Compound 1-6 in lung,kidney, and liver tissue at each of the time points. As shown in FIG.7A, the half-life of Compound 1-6 in lung, kidney, and liver was 9.4hours, 8.0 hours, and 4.3 hours, respectively. The half-life of Compound1-6 was determined by dividing ln(2) by k, the rate constant for thedecrease in Compound 1-6 concentration obtained from the slope of theplot of ln (tissue concentration) vs. time after linear regressionanalysis.

TABLE 8 Intracellular Concentration of Compound 2A TriphosphateConcentrations in Lung, Kidney, and Liver Cells Mean Intracellular TimePost Compound 1-6 Tissue Last Dose (h) Concentration (μM)¹ Lung 12 0.1424 0.037 48 0.009 Kidney 12 0.13 24 0.032 48 0.004 Liver 12 0.089 240.021 48 Not Detected ¹Calculated using non-interstitial volumes of 0.75and 0.9 mL/g lung and liver, respectively, and an assumed volume of 0.83mL/g kidney (Mandikian, D. et al. 2018 AAPS Journal 20(6):107.doi.org/10.1208/s12248-018-0264-z.)

Example 9. Prediction of Human Lung and Kidney Concentrations ofTriphosphate Compound 1-6 Based on Compound 1-6 Tissue Levels inNon-Human Primates

As described in (Good, S. S. et al. 2020 PLoS ONE 15(1):e0227104), thelevels of triphosphate Compound 1-6 in human and monkey hepatocytesincubated with 10 μM of Compound 1A were determined. FIG. 8 is a graphcomparing the levels in the two species, and as shown in the Figure,triphosphate Compound 1-6 concentrations in human hepatocytes is 7-foldgreater than in non-human primate (monkey) hepatocytes assessed byAUC₀₋₂₄ values. The data is also presented in Table 9. Using ahepatocyte volume of 3.4×10-9 mL (14) to calculate the intracellularconcentration, Compound 1-6 peaked at 8 hours in human hepatocytes at26±1 μM, while the highest concentration in monkey hepatocytes was3.1±0.1 μM at 4 hours.

TABLE 9 Intracellular Concentration of Triphosphate Concentrations inMonkey and Human Hepatocytes Mean Intracellular Incubation Compound 1-6Species Time (h) Concentration (μM)¹ Non-human 2 2.1 Primate 4 3.1 8 2.924 1.7 Human 2 14 4 22 8 26 24 17 ¹Calculated using a hepatocyte volumeof 3.4 × 10⁻⁹ mL (Lodish, H. et al. 2000 Molecular Cell Biology (fifthedition), W. H. Freeman and Co.. New York. P. 10.

Based on the ratio (7.0) of human to monkey concentrations oftriphosphate Compound 1-6 as assessed by its in vitro formation inprimary hepatocytes, the predicted human tissue level was determined.The actual tissue levels of triphosphate Compound 1-6 in monkeys and thepredicted tissue levels in humans is shown in Table 10. A clinicaldosing regimen of 1100 mg LD (loading dose)+550 mg BID (twice a day) ispredicted to achieve lung intracellular levels of triphosphate Compound1-6 at trough (12 h) above the in vitro EC₉₀ of Compound 2A againstSARS-CoV-2 replication in HAE cell cultures. Triphosphate levels duringthis dosing regimen are predicted to consistently remain above the invitro EC₉₀ of Compound 2A against SARS-CoV-2. Predictions areconservative (at least for the lung) because the ling triphosphatehalf-life in human bronchial/nasal cells (38 hours) as compared to thenon-human primate lung tissue (9.4 hours) predicts higher steady-statelevels in humans with BID dosing, but this was not factored intopredictions.

TABLE 10 Actual (Monkey) and Predicted (Human) Tissue Levels of Compound1-6 Intracellular Triphosphate 1-6 Conc. at 12 hours Post-dose (μM)Species Liver Kidney Lung Non-human primate 0.089 0.13 0.14 Human 0.620.91 0.98

Example 10. Simulation of Intracellular Concentrations of TriphosphateCompound 1-6 in Human Lung Tissue

Plasma conc-time profiles of Compound 1-7 (a surrogate for triphosphateCompound 1-6 because Compound 1-6 cannot be measured in plasma) wasobtained from subjects (N=18) who received 600 mg QD dose of Compound 2A(equivalent to 553 mg of free base Compound 1A) for 7 days as part ofthe AT-01B-001 study (as described in FIG. 1 and Table 3 of Berliba, e.et al. 2019 Antimicrob. Agents Chemother. 63(12):e01201-19). Theprofiles were subjected to population pharmacokinetic (PPK) analysisusing Monolix Suite 2019 Suite 2019 (Lixosoft, Antony, France). Theobtained PPK parameters together with the associated variance andcovariance matrices were then used to simulate, using the Simulx moduleof Monolix Suite, plasma PK profiles of Compound 1-7 for various dosingregimens.

It was assumed that 1) lung triphosphate levels of Compound 1-7 were 1.6the plasma levels of its nucleoside metabolite Compound 1-7 based on theratio obtained in monkeys for lung-to-liver concentrations of Compound1-6; and 2) the average in vitro EC₉₀ of Compound 1A against SARS-CoV-2was about 0.55 uM in HAE cell preparations. Under these assumptions, thesimulated lung Compound 1-6 levels would exceed the in vitro EC₉₀shortly after administration of a loading dose of 1100 mg and remainabove EC₉₀ with the 550 BID maintenance doses for the remaining days.The simulated lung Compound 1-6 concentration over the course of 5 daysis shown in FIG. 9 .

Additional simulations were also conducted. The kinetics of human lungCompound 1-6 levels were simulated for a Compound 2A 550 mg BID doseregimen for 5 days (FIG. 10 ) using published plasma Compound 1-7 datafrom subjects given daily 550 mg doses of Compound 2A (described inBerliba, e. et al. 2019 Antimicrob. Agents Chemother. 63(12):e01201-19)amplified by a factor of 1.6 based on the assumption that the observedlung-to-liver Compound 1-6 concentration ratio in monkeys is applicableto humans as well. The resulting predicted steady-state peak and troughlevels for the active triphosphate Compound 1-6 in human lung for thisdose regimen are 1.5 and 0.9 μM, respectively. A second approach topredicting human lung Compound 1-6 concentrations used the samesimulated plasma Compound 1-7 data but corrected the plasma values by afactor of 1.2, which is the ratio of the mean steady-state 12-h lungCompound 1-6 concentration in monkies to that of Compound 1-7 in plasma.This prediction provided respective estimates of 1.1 and 0.7 μM for peakand trough human lung triphosphate concentrations.

According to both methods, the predicted human lung levels of Compound1-6 exceed the EC₉₀ value observed against SARS-CoV-2 replication in HAEcells from within a few hours after the first dose through the end ofthe dosing period.

FIG. 10 shows the stimulated Compound 1-6 concentration in human lungusing both approaches. The solid curve represents predicted lungconcentrations of the active triphosphate Compound 1-6 metabolite aftercorrecting for the Compound 1-6 lung-to-liver concentration ratio of1.6. The dotted curve represents predicted lung concentrations of theactive triphosphate Compound 1-6 metabolite after correcting for theCompound 1-6 lung-to-Compound 1-7 plasma ratio of 1.2. The horizontalline represents the EC₉₀ of Compound 1A against SARS-CoV-2 in HAE cellsin vitro (0.47 μM).

Example 11. In Vitro Activity of Select Compounds Against SARS-CoV-2

Select compounds of the present invention were tested in a SARS-CoV-2assay. The assay was conducted using human airway epithelial (HAE;dNHBE) cells as described in Example 6. Remdesivir was the positivecontrol and the compounds were compared to Sofosbuvir. Compounds weretested in singlet using 4 serial dilutions of each compound (10, 2.5,0.625 and 0.156 μg/mL. Sofosbuvir was only tested in duplicate at 10ug/mL, Compound 1A in singlet at 1 and 0.1 ug/mL, and remdesivir insinglet at 4 serial log dilutions with top concentration of 1 ug/mL. Theresults are shown in Table 11. Compound 5 with deuterium substitution atthe 2′-position exhibited an EC₉₀ of 0.31 μM and Compound 6 with 2′-CH₂Fsubstitution exhibited an EC₉₀ of 1.8 μM. None of the compounds showedvisual toxicity.

TABLE 11 Activity of Select Compounds Against SARS-CoV-2 VYR AssayCompound EC₉₀ (μM) CC₅₀ (μM)

  Remdesivir    0.0020    0.0028    0.0030    0.0066 no visual tox novisual tox no visual tox no visual tox

  Sofosbuvir >19    no visual tox

  Compound 1A    0.63     0.46     0.52  no visual tox no visual tox novisual tox

  Compound 5    0.31  no visual tox

  Compound 6    1.8   no visual tox

  Compound 7    3.2   no visual tox

  Compound 8    6.4   no visual tox

  Compound 9    8.5   no visual tox

  Compound 10    5.3   no visual tox

  Compound 11A    3.7   no visual tox

TABLE 11B Activity of Additional Select Compounds Against SARS-CoV-2Compound VYR Assay EC₉₀ (μM)

  Compound 12 1.5

  Compound 13 3.2

  Compound 14 0.57

  Compound 15 1.1

Example 12. Formulation Description and Manufacturing of Compound 2A

A representative non-limiting batch formula for Compound 2A tablets (50mg and 100 mg) is presented in Table 12. The tablets were produced froma common blend using a direct compression process. The activepharmaceutical ingredient (API) was adjusted based on the as-is assay,with the adjustment made in the percentage of microcrystallinecellulose. The API and excipients (microcrystalline cellulose, lactosemonohydrate, and croscarmellose sodium) were screened, placed into aV-blender (PK Blendmaster, 0.5 L bowl) and mixed for 5 minutes at 25rpm. Magnesium Stearate was then screened, added and the blend was mixedfor an additional 2 minutes. The common blend was divided for use inproducing 50 mg and 100 mg tablets. The lubricated blend was thencompressed at a speed of 10 tablets/minutes using a single punchresearch tablet press (Korsch XP1) and a gravity powder feeder. The 50mg tablets were produced using round standard concave 6 mm tooling and3.5 kN forces. The 100 mg tablets were produced using 8 mm roundstandard concave tooling and 3.9-4.2 kN forces.

TABLE 12 Formulation of 50 mg and 100 mg Compound 2 Tablets Mg/unit 50mg 100 mg Raw Material % w/w g/batch Tablet Tablet Compound 2A 50.0180.0 50.0 100.0 Microcrystalline 20.0 72.0 20.0 40.0 Cellulose, USP/NF,EP Lactose Monohydrate, 24.0 86.4 24.0 48.0 USP/NF, BP, EP, JPCroscarmellose Sodium, 5.0 18.0 5.0 10.0 USP/NF, EP Magnesium Stearate,1.0 3.6 1.0 2.0 USP/NF, BP, EP JP Total 100.0 200.0

Compound 2A was adjusted based on the as-is assay, with the adjustmentmade in the percentage of microcrystalline cellulose. Compound 2A andexcipients (microcrystalline cellulose, lactose monohydrate, andcroscarmellose sodium) were screened, placed into a V-blender (PKBlendmaster, 0.5 L bowl) and mixed for 5 minutes at 25 rpm. Magnesiumstearate was then screened, added and the blend was mixed for anadditional 2 minutes. The common blend was divided for use in producing50 mg and 100 mg tablets. The lubricated blend was then compressed at aspeed of 10 tablets/minutes using a single punch research tablet press(Korsch XP1) and a gravity powder feeder. The 50 mg tablets wereproduced using round standard concave 6 mm tooling and 3.5 kN forces.The 100 mg tablets were produced using 8 mm round standard concavetooling and 3.9-4.2 kN forces. The specifications of the 50 mg and 100mg tablets are shown in Table 13.

TABLE 13 Specifications of 50 mg and 100 mg Tablets of Compound 2A 50 mgTablets 100 mg Tablets Average Weight (n = 10) 100 ± 5 mg  200 ± 10 mgIndividual Weight 100 ± 10 mg 200 ± 20 mg Hardness 5.3 kp 8.3 kpDisintegration <15 minutes <15 minutes Friability NMT 0.5% NMT 0.5%

The 50 mg and 100 mg tablets produced as described above were subjectedto 6 month stability studies under three conditions: 5° C.(refrigeration), 25° C./60% RH (ambient), and 40° C./75% RH(accelerated). Both the 50 mg and 100 mg tablets were chemically stableunder all three conditions tested.

Under refrigeration conditions (5° C.), both the 50 mg and 100 mgtablets remained white solids that did not change in appearance from T=0to T=6 months. Throughout the 6-month study, no impurities were reportedthat were greater than 0.05% for either the 50 mg tablets or the 100 mgtablets. The water content after 6 months was also less than 3.0% w/wfor both tablets. Similar results were reported when the tablets weresubjected to ambient conditions (25° C./60% RH); no impurities that weregreater than 0.05% were reported throughout the 6 months for bothtablets and the water content did not exceed 3.0% w/w at the 6-monthmark. When the tablets were subjected to accelerated conditions (40°C./75% RH), the appearance of the 50 mg and 100 mg tablets did notchange from a white, round tablet. One impurity was reported after 3months, but the impurity was only 0.09%. A second impurity was reportedafter 6 months, but the total impurity percentage was only 0.21% forboth the 50 mg and 100 mg tablets. Water content was 3.4% w/w at 6months for the 50 mg tablets and 3.2% w/w for the 100 mg tablets.

In a separate study, the stability of 50 mg and 100 mg tablets ofCompound 2A at ambient conditions (25° C./60% RH) was measured over 9months. The appearance of the 50 mg and 100 mg tablet did not changefrom a white round tablet over the course of 9 months. Impurities in the50 mg tablet were less than 0.10% after 9 months and impurities in the100 mg tablet were less than 0.05%. The water content of the 50 mgtablet and the 100 mg tablet after 9 months was only 2.7% w/w and 2.6%w/w, respectively.

This specification has been described with reference to embodiments ofthe invention. Given the teaching herein, one of ordinary skill in theart will be able to modify the invention for a desired purpose and suchvariations are considered within the scope of the invention.

What is claimed is:
 1. A method for the treatment of COVID-19 caused bythe SARS-CoV-2 virus in a human host in need thereof comprisingadministering an effective amount of a compound of Formula I:

or a pharmaceutically acceptable salt thereof, optionally in apharmaceutically acceptable carrier, wherein: R¹ is methyl; R² is aryl,or aryl(C₁-C₄alkyl); R³ is hydrogen or C₁₋₆alkyl; R^(4a) and R^(4b) areindependently selected from hydrogen, C₁₋₆alkyl, and C₃₋₇cycloalkyl; andR⁵ is C₁₋₆alkyl, C₁₋₆haloalkyl, C₃₋₇cycloalkyl, aryl(C₁-C₄alkyl)-, aryl,heteroaryl, or heteroalkyl.
 2. The method of claim 1, wherein: R² isphenyl; R³ is hydrogen; R^(4a) is methyl; and R^(4b) is hydrogen.
 3. Themethod of claim 1, wherein: R² is phenyl; R³ is hydrogen; R^(4a) ismethyl; R^(4b) is hydrogen; and the phosphoramidate is in theS_(p)-configuration.
 4. The method of claim 1, wherein: R² is phenyl; R³is hydrogen; R^(4a) is methyl; R^(4b) is hydrogen; and thephosphoramidate is in the R_(p)-configuration.
 5. The method of claim 1,wherein R² is aryl.
 6. The method of claim 1, wherein R³ is hydrogen. 7.The method of claim 1, wherein R^(4a) is methyl and R^(4b) is hydrogen.8. The method of claim 1, wherein R⁵ is C₁₋₆alkyl.
 9. The method ofclaim 1, wherein R⁵ is isopropyl.
 10. The method of claim 1, wherein thecompound of Formula I, or a pharmaceutically acceptable salt thereof,with the pharmaceutically acceptable carrier is in a dosage formsuitable for oral administration.
 11. The method of claim 10, whereinthe dosage form is a solid dosage form.
 12. The method of claim 11,wherein the solid dosage form is a tablet or capsule.
 13. The method ofclaim 10, wherein the dosage form is a liquid dosage form.
 14. Themethod of claim 13, wherein the liquid dosage form is a solution or asuspension.
 15. The method of claim 1, wherein the compound of FormulaI, or a pharmaceutically acceptable salt thereof, with thepharmaceutically acceptable carrier is in a dosage form suitable forintravenous administration.
 16. The method of claim 1, wherein thecompound of Formula I, or a pharmaceutically acceptable salt thereof,with the pharmaceutically acceptable carrier is in a dosage formsuitable for parenteral administration.
 17. The method of claim 1,wherein the compound is administered for at least one week.
 18. Themethod of claim 1, wherein the compound is administered for about fivedays.
 19. The method of claim 1, wherein the compound is administeredtwice a day for about five days.
 20. The method of claim 1, wherein thecompound is administered once a day.
 21. The method of claim 1, whereinthe compound is administered twice a day.
 22. The method of claim 1,wherein the compound is administered three times a day.
 23. The methodof claim 1, wherein at least about 500 mg of the compound isadministered.
 24. The method of claim 1, wherein at least about 550 mgof the compound is administered.
 25. The method of claim 1, wherein 550mg of the compound of Formula I without a pharmaceutically acceptablesalt is administered twice a day for about five days.
 26. The method ofclaim 1, wherein R² is aryl(C₁₋₄alkyl)-.
 27. The method of claim 1,wherein R² is benzyl.
 28. The method of claim 1, wherein R² is naphthyl.29. The method of claim 1, wherein R⁵ is ethyl.
 30. The method of claim1, wherein R⁵ is tert-pentyl.
 31. The method of claim 1, wherein R⁵ isbenzyl.
 32. The method of claim 1, wherein R⁵ is naphthyl.
 33. Themethod of claim 1, wherein R⁵ is cyclohexyl.
 34. The method of claim 1,wherein R⁵ is aryl.
 35. The method of claim 1, wherein the compound isadministered for at least five days.
 36. The method of claim 1, whereinthe pharmaceutically acceptable salt is a hemisulfate salt.
 37. Themethod of claim 36, wherein 600 mg of the hemisulfate salt of a compoundof Formula I is administered twice a day for about five days.